fix runtime TEXMFHOME usage for context mkiv

git-svn-id: svn://tug.org/texlive/trunk@23079 c570f23f-e606-0410-a88d-b1316a301751

27 files changed, 840 insertions, 384 deletions

diff --git a/Build/source/texk/texlive/context/mtxrun b/Build/source/texk/texlive/context/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Build/source/texk/texlive/context/mtxrun
+++ b/Build/source/texk/texlive/context/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/alpha-linux/mtxrun b/Master/bin/alpha-linux/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/alpha-linux/mtxrun
+++ b/Master/bin/alpha-linux/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/amd64-freebsd/mtxrun b/Master/bin/amd64-freebsd/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/amd64-freebsd/mtxrun
+++ b/Master/bin/amd64-freebsd/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/amd64-kfreebsd/mtxrun b/Master/bin/amd64-kfreebsd/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/amd64-kfreebsd/mtxrun
+++ b/Master/bin/amd64-kfreebsd/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/i386-cygwin/mtxrun b/Master/bin/i386-cygwin/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/i386-cygwin/mtxrun
+++ b/Master/bin/i386-cygwin/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/i386-freebsd/mtxrun b/Master/bin/i386-freebsd/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/i386-freebsd/mtxrun
+++ b/Master/bin/i386-freebsd/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/i386-kfreebsd/mtxrun b/Master/bin/i386-kfreebsd/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/i386-kfreebsd/mtxrun
+++ b/Master/bin/i386-kfreebsd/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/i386-linux/mtxrun b/Master/bin/i386-linux/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/i386-linux/mtxrun
+++ b/Master/bin/i386-linux/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/i386-netbsd/mtxrun b/Master/bin/i386-netbsd/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/i386-netbsd/mtxrun
+++ b/Master/bin/i386-netbsd/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/i386-solaris/mtxrun b/Master/bin/i386-solaris/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/i386-solaris/mtxrun
+++ b/Master/bin/i386-solaris/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/mips-irix/mtxrun b/Master/bin/mips-irix/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/mips-irix/mtxrun
+++ b/Master/bin/mips-irix/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/powerpc-aix/mtxrun b/Master/bin/powerpc-aix/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/powerpc-aix/mtxrun
+++ b/Master/bin/powerpc-aix/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/powerpc-linux/mtxrun b/Master/bin/powerpc-linux/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/powerpc-linux/mtxrun
+++ b/Master/bin/powerpc-linux/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/sparc-linux/mtxrun b/Master/bin/sparc-linux/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/sparc-linux/mtxrun
+++ b/Master/bin/sparc-linux/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/sparc-solaris/mtxrun b/Master/bin/sparc-solaris/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/sparc-solaris/mtxrun
+++ b/Master/bin/sparc-solaris/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/universal-darwin/mtxrun b/Master/bin/universal-darwin/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/universal-darwin/mtxrun
+++ b/Master/bin/universal-darwin/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/win32/mtxrun.lua b/Master/bin/win32/mtxrun.lua
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/win32/mtxrun.lua
+++ b/Master/bin/win32/mtxrun.lua
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/x86_64-darwin/mtxrun b/Master/bin/x86_64-darwin/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/x86_64-darwin/mtxrun
+++ b/Master/bin/x86_64-darwin/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/x86_64-linux/mtxrun b/Master/bin/x86_64-linux/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/x86_64-linux/mtxrun
+++ b/Master/bin/x86_64-linux/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/bin/x86_64-solaris/mtxrun b/Master/bin/x86_64-solaris/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/bin/x86_64-solaris/mtxrun
+++ b/Master/bin/x86_64-solaris/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/texmf-dist/scripts/context/lua/mtxrun.lua b/Master/texmf-dist/scripts/context/lua/mtxrun.lua
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/texmf-dist/scripts/context/lua/mtxrun.lua
+++ b/Master/texmf-dist/scripts/context/lua/mtxrun.lua
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/texmf-dist/scripts/context/stubs/mswin/mtxrun.lua b/Master/texmf-dist/scripts/context/stubs/mswin/mtxrun.lua
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/texmf-dist/scripts/context/stubs/mswin/mtxrun.lua
+++ b/Master/texmf-dist/scripts/context/stubs/mswin/mtxrun.lua
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/texmf-dist/scripts/context/stubs/unix/mtxrun b/Master/texmf-dist/scripts/context/stubs/unix/mtxrun
index f90dbfbd7d1..40c61ef000c 100755
--- a/Master/texmf-dist/scripts/context/stubs/unix/mtxrun
+++ b/Master/texmf-dist/scripts/context/stubs/unix/mtxrun
@@ -2829,8 +2829,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing
@@ -10651,7 +10651,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+		    -- file.is_writable() is not really important here, since this
+		    -- branch is only checked for as-yet non-existent paths, and
+		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
@@ -11491,10 +11495,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -12127,22 +12136,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
@@ -13400,7 +13418,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/texmf-dist/tex/context/base/data-res.lua b/Master/texmf-dist/tex/context/base/data-res.lua
index c3bb5bd48ab..33b1fe65274 100644
--- a/Master/texmf-dist/tex/context/base/data-res.lua
+++ b/Master/texmf-dist/tex/context/base/data-res.lua
@@ -411,10 +411,15 @@ local function locate_file_databases()
                 local runtime = stripped == path
                 path = resolvers.cleanpath(path)
                 local spec = resolvers.splitmethod(stripped)
-                if spec.scheme == "cache" or spec.scheme == "file" then
-                    stripped = spec.path
-                elseif runtime and (spec.noscheme or spec.scheme == "file") then
+                -- TH Original did this the other way around (elseif and if tests
+                -- reversed) but then the else branch was never reached, as 'runtime'
+                -- would effectively be ignored. In turn, that meant that the wrong
+                -- locator method was used, such that tree: and file: were treated 
+		-- identically (cached and no runtime search).
+                if runtime and (spec.noscheme or spec.scheme == "file") then
                     stripped = "tree:///" .. stripped
+                elseif spec.scheme == "cache" or spec.scheme == "file" then
+                    stripped = spec.path
                 end
                 if trace_locating then
                     if runtime then
@@ -1047,22 +1052,31 @@ local function collect_instance_files(filename,askedformat,allresults) -- todo :
                 end
                 if not done and doscan then
                     -- check if on disk / unchecked / does not work at all / also zips
+                    -- TH perhaps it did not work because of missing resolvers.resolve() 
+                    -- and resolvers.scanfiles() calls ...
+                    pathname = resolvers.resolve(pathname)
                     local scheme = url.hasscheme(pathname)
                     if not scheme or scheme == "file" then
                         local pname = gsub(pathname,"%.%*$",'')
                         if not find(pname,"%*") then
                             local ppname = gsub(pname,"/+$","")
                             if can_be_dir(ppname) then
-                                for k=1,#wantedfiles do
-                                    local w = wantedfiles[k]
-                                    local fname = filejoin(ppname,w)
-                                    if isreadable(fname) then
-                                        if trace_detail then
-                                            report_resolving("found '%s' by scanning",fname)
+                                local files = resolvers.scanfiles(ppname)
+                                if files then 
+                                    for k=1,#wantedfiles do
+                                        local w = wantedfiles[k]
+                                        local subpath = files[w]
+                                        if subpath then
+                                            local fname = filejoin(ppname,subpath,w)
+                                            if isreadable(fname) then
+                                                if trace_detail then
+                                                    report_resolving("found '%s' by scanning",fname)
+                                                end
+                                                result[#result+1] = fname
+                                                done = true
+                                                if not allresults then break end
+                                            end
                                         end
-                                        result[#result+1] = fname
-                                        done = true
-                                        if not allresults then break end
                                     end
                                 end
                             else
diff --git a/Master/texmf-dist/tex/context/base/data-tmp.lua b/Master/texmf-dist/tex/context/base/data-tmp.lua
index ec6f91e24da..46c9b306283 100644
--- a/Master/texmf-dist/tex/context/base/data-tmp.lua
+++ b/Master/texmf-dist/tex/context/base/data-tmp.lua
@@ -85,7 +85,11 @@ local function identify()
                     end
                 elseif not writable and caches.force then
                     local cacheparent = file.dirname(cachepath)
-                    if file.is_writable(cacheparent) then
+                    -- TH: added 'or true' for deeply buried non-existent caches. 
+ 		    -- file.is_writable() is not really important here, since this
+ 		    -- branch is only checked for as-yet non-existent paths, and
+ 		    -- it guards against mkdirs() failing, anyway.
+                    if file.is_writable(cacheparent) or true then
                         if not caches.ask or io.ask(format("\nShould I create the cache path %s?",cachepath), "no", { "yes", "no" }) == "yes" then
                             mkdirs(cachepath)
                             if isdir(cachepath) and file.is_writable(cachepath) then
diff --git a/Master/texmf-dist/tex/context/base/data-tre.lua b/Master/texmf-dist/tex/context/base/data-tre.lua
index 88bf4f11275..8b72f046bfc 100644
--- a/Master/texmf-dist/tex/context/base/data-tre.lua
+++ b/Master/texmf-dist/tex/context/base/data-tre.lua
@@ -47,7 +47,8 @@ function resolvers.finders.tree(specification)
 end
 
 function resolvers.locators.tree(specification)
-    local name = specification.filename
+    -- TH: resolvers.resolve() call was missing here
+    local name = resolvers.resolve(specification.filename)
     if name ~= '' and lfs.isdir(name) then
         if trace_locating then
             report_trees("locator '%s' found",name)
diff --git a/Master/texmf-dist/tex/context/base/l-url.lua b/Master/texmf-dist/tex/context/base/l-url.lua
index d75135a2abe..ffd0ac5b54e 100644
--- a/Master/texmf-dist/tex/context/base/l-url.lua
+++ b/Master/texmf-dist/tex/context/base/l-url.lua
@@ -46,8 +46,8 @@ local escaped     = (plus / " ") + (percent * C(hexdigit * hexdigit) / tochar)
 
 -- we assume schemes with more than 1 character (in order to avoid problems with windows disks)
 
-local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon + nothing
-local authority = slash * slash * Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
+local scheme    =                 Cs((escaped+(1-colon-slash-qmark-hash))^2) * colon * slash * slash + nothing
+local authority =                 Cs((escaped+(1-      slash-qmark-hash))^0)         + nothing
 local path      = slash *         Cs((escaped+(1-            qmark-hash))^0)         + nothing
 local query     = qmark         * Cs((escaped+(1-                  hash))^0)         + nothing
 local fragment  = hash          * Cs((escaped+(1-           endofstring))^0)         + nothing