diff mercurial/copies.py @ 44237:b4057d001760

merge: when rename was made on both sides, use ancestor as merge base

When both sides of a merge have renamed a file to the same place, we
would treat that as a "both created" action in merge.py. That means
that we'd use an empty diffbase. It seems better to use the copy
source as diffbase. That can be done by simply dropping code that
prevented us from doing that. I think I did it that way in
57203e0210f8 (copies: calculate mergecopies() based on pathcopies(),
2019-04-11) only to preserve the existing behavior. I also suspect it
was just an accident that it behaved that way before that commit.

Note that until fa9ad1da2e77 (merge: start using the per-side copy
dicts, 2020-01-23), it was non-deterministic (depending on iteration
order of the `allsources` set in `copies._fullcopytracing()`) which
source was used in the affected test case in test-rename-merge1.t. We
could easily have fixed that by sorting them, but now we can instead
detect the case (the TODO added in the previous patch).

Differential Revision: https://phab.mercurial-scm.org/D7974

--- a/mercurial/copies.py	Fri Jan 31 08:47:32 2020 -0800
+++ b/mercurial/copies.py	Wed Jan 22 13:29:26 2020 -0800
@@ -537,10 +537,7 @@
             return
         # modified on side 2
         for dst in dsts1:
-            if dst not in m2:
-                # dst not added on side 2 (handle as regular
-                # "both created" case in manifestmerge otherwise)
-                copy[dst] = src
+            copy[dst] = src
 
 
 class branch_copies(object):