[PATCH 2 of 8] cachevfs: add a vfs dedicated to cache

[Boris Feld]

# HG changeset patch
# User Boris Feld <boris.feld at octobus.net>
# Date 1500152704 -7200
#      Sat Jul 15 23:05:04 2017 +0200
# Node ID 76e3839204e5bacf6e894a695853a9498ebe22d7
# Parent  a73c1ffd2edb211d19242a60027f84cf50d88fa4
# EXP-Topic cachevfs
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.

diff -r a73c1ffd2edb -r 76e3839204e5 mercurial/localrepo.py
--- 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
diff -r a73c1ffd2edb -r 76e3839204e5 mercurial/statichttprepo.py
--- a/mercurial/statichttprepo.py	Sat Jul 15 22:40:51 2017 +0200
+++ b/mercurial/statichttprepo.py	Sat Jul 15 23:05:04 2017 +0200
@@ -124,6 +124,7 @@
 
         vfsclass = build_opener(ui, authinfo)
         self.vfs = vfsclass(self.path)
+        self.cachevfs = vfsclass(self.vfs.join('cache'))
         self._phasedefaults = []
 
         self.names = namespaces.namespaces()