[PATCH 2 of 2 rfc] diff: search beyond ancestor when detecting renames

[Mads Kiilerich]

# HG changeset patch
# User Mads Kiilerich <madski at unity3d.com>
# Date 1383878972 -3600
#      Fri Nov 08 03:49:32 2013 +0100
# Branch stable
# Node ID 79b83373ff5e66b61eaccafa3fc2bd7487e06476
# Parent  d3df4d706b86fa1780f6156a033062a7f617cd4c
diff: search beyond ancestor when detecting renames

This removes an optimization that was introduced in 91eb4512edd0 but seems to
be too aggressive - as indicated by how it changed test-mq-merge.t .

Removing the optimization will in some cases give a different and arguably more
correct result. It will probably also introduce a significant performance
regression in other cases.

diff --git a/mercurial/copies.py b/mercurial/copies.py
--- a/mercurial/copies.py
+++ b/mercurial/copies.py
@@ -100,14 +100,11 @@
 
 def _tracefile(fctx, actx):
     '''return file context that is the ancestor of fctx present in actx'''
-    stop = actx.rev()
     am = actx.manifest()
 
     for f in fctx.ancestors():
         if am.get(f.path(), None) == f.filenode():
             return f
-        if f.rev() < stop:
-            return None
 
 def _dirstatecopies(d):
     ds = d._repo.dirstate
diff --git a/tests/test-copied-diff.t b/tests/test-copied-diff.t
--- a/tests/test-copied-diff.t
+++ b/tests/test-copied-diff.t
@@ -49,25 +49,16 @@
   |/
   o  f=0
   
-Diff from "other" to tip do not see the rename:
+Diff from "other" to tip do see the rename:
 
   $ hg diff --git -r 2 -r tip
-  diff --git a/f b/f
-  deleted file mode 100644
-  --- a/f
-  +++ /dev/null
-  @@ -1,1 +0,0 @@
-  -0
-  diff --git a/g b/g
-  new file mode 100644
-  --- /dev/null
-  +++ b/g
-  @@ -0,0 +1,1 @@
-  +0
+  diff --git a/f b/g
+  rename from f
+  rename to g
 
   $ cd ..
 
-Diff from "other" to diff with another topological ordering do see the rename:
+Diff from "other" to diff with another topological ordering also see the rename:
 
   $ hg clone -q -U repo1 repo2 -r 5
   $ cd repo2
diff --git a/tests/test-mq-merge.t b/tests/test-mq-merge.t
--- a/tests/test-mq-merge.t
+++ b/tests/test-mq-merge.t
@@ -147,11 +147,13 @@
   -b
   +a
   +c
-  diff --git a/aa b/aa
-  new file mode 100644
-  --- /dev/null
+  diff --git a/a b/aa
+  copy from a
+  copy to aa
+  --- a/a
   +++ b/aa
-  @@ -0,0 +1,1 @@
+  @@ -1,1 +1,1 @@
+  -b
   +a
 
 Check patcha2 is still a regular patch: