diff mercurial/dirstateguard.py @ 33619:609606d21765

rebase: use one dirstateguard for when using rebase.singletransaction

This was previously landed as 2519994d25ca but backed out in b63351f6a2 because
it broke hooks mid-rebase and caused conflict resolution data loss in the event
of unexpected exceptions. This new version adds the behavior back but behind a
config flag, since the performance improvement is notable in large repositories.

The old commit message was:

Recently we switched rebases to run the entire rebase inside a single
transaction, which dramatically improved the speed of rebases in repos with
large working copies. Let's also move the dirstate into a single dirstateguard
to get the same benefits. This let's us avoid serializing the dirstate after
each commit.

In a large repo, rebasing 27 commits is sped up by about 20%.

I believe the test changes are because us touching the dirstate gave the
transaction something to actually rollback.
(grafted from 9e3dc3a1638b9754b58a0cb26aaa75d868058109)
(grafted from 7d38b41d2266d9a02a15c64229fae0da5738dcec)

Differential Revision: https://phab.mercurial-scm.org/D135

--- a/mercurial/dirstateguard.py	Tue Aug 01 10:14:25 2017 -0400
+++ b/mercurial/dirstateguard.py	Thu Jul 20 01:30:41 2017 -0700
@@ -43,6 +43,16 @@
             # ``release(tr, ....)``.
             self._abort()
 
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        try:
+            if exc_type is None:
+                self.close()
+        finally:
+            self.release()
+
     def close(self):
         if not self._active: # already inactivated
             msg = (_("can't close already inactivated backup: %s")