revbranchcache: write cache even during read operations

Previously we would only actually write the revbranchcache to disk if we were in
the middle of a write operation (like commit). Now we will also write it during
any read operation. The cache knows how to invalidate itself, so it shouldn't
become corrupt if multiple writers try at once (and the write-on-read
behavior/risk is the same as all our other caches).

mercurial/branchmap.py

@@ -97,9 +97,6 def updatecache(repo):
         partial.update(repo, revs)
         partial.write(repo)
 
-    if repo._revbranchcache is not None:
-        repo._revbranchcache.write()
-
     assert partial.validfor(repo), filtername
     repo._branchcaches[repo.filtername] = partial
 

mercurial/localrepo.py

@@ -303,7 +303,11 class localrepository(object):
         self.names = namespaces.namespaces()
 
     def close(self):
-        pass
+        self._writecaches()
+
+    def _writecaches(self):
+        if self._revbranchcache:
+            self._revbranchcache.write()
 
     def _restrictcapabilities(self, caps):
         # bundle2 is not ready for prime time, drop it unless explicitly

tests/test-branches.t

@@ -561,8 +561,8 no errors when revbranchcache is not wri
 recovery from invalid cache revs file with trailing data
   $ echo >> .hg/cache/rbc-revs-v1
   $ rm -f .hg/cache/branch* && hg head a -T '{rev}\n' --debug
+  5
   truncating cache/rbc-revs-v1 to 120
-  5
   $ f --size .hg/cache/rbc-revs*
   .hg/cache/rbc-revs-v1: size=120
 recovery from invalid cache file with partial last record
@@ -571,8 +571,8 recovery from invalid cache file with pa
   $ f --size .hg/cache/rbc-revs*
   .hg/cache/rbc-revs-v1: size=119
   $ rm -f .hg/cache/branch* && hg head a -T '{rev}\n' --debug
+  5
   truncating cache/rbc-revs-v1 to 112
-  5
   $ f --size .hg/cache/rbc-revs*
   .hg/cache/rbc-revs-v1: size=120
 recovery from invalid cache file with missing record - no truncation
@@ -590,11 +590,11 recovery from invalid cache file with so
   $ f -qDB 112 rbc-revs-v1 >> .hg/cache/rbc-revs-v1
   $ f --size .hg/cache/rbc-revs*
   .hg/cache/rbc-revs-v1: size=120
-  $ hg log -r 'branch(.)' -T '{rev} '
-  3 4 8 9 10 11 12 13  (no-eol)
+  $ hg log -r 'branch(.)' -T '{rev} ' --debug
+  3 4 8 9 10 11 12 13 truncating cache/rbc-revs-v1 to 8
   $ rm -f .hg/cache/branch* && hg head a -T '{rev}\n' --debug
-  truncating cache/rbc-revs-v1 to 8
   5
+  truncating cache/rbc-revs-v1 to 104
   $ f --size --hexdump --bytes=16 .hg/cache/rbc-revs*
   .hg/cache/rbc-revs-v1: size=120
   0000: 19 70 9c 5a 00 00 00 00 dd 6b 44 0d 00 00 00 01 |.p.Z.....kD.....|

tests/test-rebase-conflicts.t

@@ -322,6 +322,6 Check that the right ancestors is used w
   files: 1/1 chunks (100.00%)
   added 2 changesets with 2 changes to 1 files
   invalid branchheads cache (served): tip differs
-  truncating cache/rbc-revs-v1 to 72
   rebase completed
   updating the branch cache
+  truncating cache/rbc-revs-v1 to 72