cachevfs: add a vfs dedicated to cache Most of the cache content lives in '.hg/cache/'. Moreover they are computed exclusively from data in the '.hg/store' directory. This creates issues with the share extension as the '.hg/store' directory is shared but the '.hg/cache' is not. On large repositories, this makes this prevent some usage of the share extension inefficient as some caches can take minutes to be recomputed. To improve the situation, we introduce a new 'cachevfs' that will be dedicated to cache reading and writing. In the next patches of this series, we'll migrate the 4 existing caches to it and update the share extension.

--- a/mercurial/localrepo.py	Sat Jul 15 22:40:51 2017 +0200
+++ b/mercurial/localrepo.py	Sat Jul 15 23:05:04 2017 +0200
@@ -423,6 +423,8 @@
         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.createmode = self.store.createmode
         if (self.ui.configbool('devel', 'all-warnings') or
             self.ui.configbool('devel', 'check-locks')):
             if util.safehasattr(self.svfs, 'vfs'): # this is filtervfs