diff tests/test-generaldelta.t @ 27251:d9bfe6289acf

revlog: don't consider nullrev when choosing delta base

In the most complex case, we try using the incoming delta base, then
we try both parents, and then we try the previous revlog entry. If
none of these result in a good delta, we natually use the null
revision as base. However, we sometimes consider the nullrev before we
have exhausted our other options. Specifically, when both parents are
null, we use the nullrev as delta base if it produces a good delta
(according to _isgooddelta()), and we fail to try the previous revlog
entry as delta base. After 20a9226bdc8a (addrevision: use general
delta when the incoming base delta is bad, 2015-12-01), it can also
happen for non-merge commits when the incoming delta is not good.

The Firefox repo (from many months back) shrinks a tiny bit with this
patch: from 1.855GB to 1.830GB (1.4%). The hg repo itself shrinks even
less: by less than 0.1%. There may be repos that get larger instead.

This undoes the unexplained test change in 20a9226bdc8a.

--- a/tests/test-generaldelta.t	Fri Dec 04 17:14:14 2015 -0800
+++ b/tests/test-generaldelta.t	Fri Dec 04 17:46:56 2015 -0800
@@ -133,8 +133,8 @@
   $ hg debugindex -m
      rev    offset  length  delta linkrev nodeid       p1           p2
        0         0      59     -1       0 8dde941edb6e 000000000000 000000000000
-       1        59      59     -1       1 315c023f341d 000000000000 000000000000
-       2       118      65      1       2 2ab389a983eb 315c023f341d 8dde941edb6e
+       1        59      61      0       1 315c023f341d 000000000000 000000000000
+       2       120      65      1       2 2ab389a983eb 315c023f341d 8dde941edb6e
 
   $ hg strip -q -r . --config extensions.strip=
 
@@ -145,8 +145,8 @@
   $ hg debugindex -m
      rev    offset  length  delta linkrev nodeid       p1           p2
        0         0      59     -1       0 8dde941edb6e 000000000000 000000000000
-       1        59      59     -1       1 315c023f341d 000000000000 000000000000
-       2       118      62      0       2 2ab389a983eb 315c023f341d 8dde941edb6e
+       1        59      61      0       1 315c023f341d 000000000000 000000000000
+       2       120      62      0       2 2ab389a983eb 315c023f341d 8dde941edb6e
 
 Test that strip bundle use bundle2
   $ hg --config extensions.strip= strip .