share: share 'cachevfs' with the source clone (issue5108)

share: share 'cachevfs' with the source clone (issue5108)

Share extension now also share caches reads and writes. Not sharing caches
results in costly caches recomputations which can takes up to minutes when
using shares on large repositories.

There are a couple of file in the '.hg/cache/' that depends of the current
visibility. Visibility can be affected by the working copy location, something
which is specific to each share. We ignores them for this series because they:

* are the minority,
* already have a good fallback to other precomputed caches,
* are only affected when people use the experimental evolution feature.

--- a/mercurial/localrepo.py	Sat Jul 15 23:05:15 2017 +0200
+++ b/mercurial/localrepo.py	Sat Jul 15 23:49:22 2017 +0200
@@ -402,12 +402,14 @@
                 if inst.errno != errno.ENOENT:
                     raise
 
+        cachepath = self.vfs.join('cache')
         self.sharedpath = self.path
         try:
             sharedpath = self.vfs.read("sharedpath").rstrip('\n')
             if 'relshared' in self.requirements:
                 sharedpath = self.vfs.join(sharedpath)
             vfs = vfsmod.vfs(sharedpath, realpath=True)
+            cachepath = vfs.join('cache')
             s = vfs.base
             if not vfs.exists():
                 raise error.RepoError(
@@ -423,7 +425,7 @@
         self.svfs = self.store.vfs
         self.sjoin = self.store.join
         self.vfs.createmode = self.store.createmode
-        self.cachevfs = vfsmod.vfs(self.vfs.join('cache'))
+        self.cachevfs = vfsmod.vfs(cachepath)
         self.cachevfs.createmode = self.store.createmode
         if (self.ui.configbool('devel', 'all-warnings') or
             self.ui.configbool('devel', 'check-locks')):

--- a/tests/test-share.t	Sat Jul 15 23:05:15 2017 +0200
+++ b/tests/test-share.t	Sat Jul 15 23:49:22 2017 +0200
@@ -24,6 +24,20 @@
   $ test -d .hg/store
   [1]
 
+share shouldn't have a cache dir, original repo should
+
+  $ hg branches
+  default                        0:d3873e73d99e
+  $ hg tags
+  tip                                0:d3873e73d99e
+  $ test -d .hg/cache
+  [1]
+  $ ls -1 ../repo1/.hg/cache
+  branch2-served
+  rbc-names-v1
+  rbc-revs-v1
+  tags2-visible
+
 Some sed versions appends newline, some don't, and some just fails
 
   $ cat .hg/sharedpath; echo