checkexec: create destination directory if necessary

Since 460733327640, a "share" use the cache of the source repository. A side
effect is that no `.hg/cache` directory exists in the "share" anymore. As a
result, the checkexec logic can't use it to create its temporary file and have
to use the working copy for that.

This is suboptimal, it pollutes the working copy and prevents them to keep the
file around in cache. We do not want to use the cache directory for the share
target, it might be on a different file system.

So instead, we (try to) create the directory if it is missing. This is a
simple change that fixes the current behavior regression on stable.

On default, we should probably ensure the proper directories are created when
initializing the repository. We should also introduce a 'wcache' directory to
hold cache file related to the working copy. This would clarify the cache
situation regarding shares.

The tests catch a couple of other affected cases.

mercurial/posix.py

@@ -181,7 +181,22 b' def checkexec(path):'
 
     try:
         EXECFLAGS = stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH
-        cachedir = os.path.join(path, '.hg', 'cache')
+        basedir = os.path.join(path, '.hg')
+        cachedir = os.path.join(basedir, 'cache')
+        storedir = os.path.join(basedir, 'store')
+        if not os.path.exists(cachedir):
+            try:
+                # we want to create the 'cache' directory, not the '.hg' one.
+                # Automatically creating '.hg' directory could silently spawn
+                # invalid Mercurial repositories. That seems like a bad idea.
+                os.mkdir(cachedir)
+                if os.path.exists(storedir):
+                    copymode(storedir, cachedir)
+                else:
+                    copymode(basedir, cachedir)
+            except (IOError, OSError):
+                # we other fallback logic triggers
+                pass
         if os.path.isdir(cachedir):
             checkisexec = os.path.join(cachedir, 'checkisexec')
             checknoexec = os.path.join(cachedir, 'checknoexec')

tests/test-fncache.t

@@ -88,6 +88,9 b' Non store repo:'
   .hg/00manifest.i
   .hg/cache
   .hg/cache/branch2-served
+  .hg/cache/checkisexec
+  .hg/cache/checklink
+  .hg/cache/checklink-target
   .hg/cache/manifestfulltextcache (reporevlogstore !)
   .hg/cache/rbc-names-v1
   .hg/cache/rbc-revs-v1
@@ -122,6 +125,9 b' Non fncache repo:'
   .hg/00changelog.i
   .hg/cache
   .hg/cache/branch2-served
+  .hg/cache/checkisexec
+  .hg/cache/checklink
+  .hg/cache/checklink-target
   .hg/cache/manifestfulltextcache (reporevlogstore !)
   .hg/cache/rbc-names-v1
   .hg/cache/rbc-revs-v1

tests/test-inherit-mode.t

@@ -69,6 +69,9 b' new directories are setgid'
   00600 ./.hg/00changelog.i
   00770 ./.hg/cache/
   00660 ./.hg/cache/branch2-served
+  00711 ./.hg/cache/checkisexec
+  00777 ./.hg/cache/checklink
+  00600 ./.hg/cache/checklink-target
   00660 ./.hg/cache/manifestfulltextcache (reporevlogstore !)
   00660 ./.hg/cache/rbc-names-v1
   00660 ./.hg/cache/rbc-revs-v1

tests/test-share.t

@@ -22,16 +22,21 b" share shouldn't have a store dir"
   $ test -d .hg/store
   [1]
 
-share shouldn't have a cache dir, original repo should
+share shouldn't have a full cache dir, original repo should
 
   $ hg branches
   default                        0:d3873e73d99e
   $ hg tags
   tip                                0:d3873e73d99e
-  $ test -d .hg/cache
-  [1]
+  $ ls -1 .hg/cache
+  checkisexec
+  checklink
+  checklink-target
   $ ls -1 ../repo1/.hg/cache
   branch2-served
+  checkisexec
+  checklink
+  checklink-target
   manifestfulltextcache (reporevlogstore !)
   rbc-names-v1
   rbc-revs-v1