[PATCH] localrepo: prevent executable-bit only changes from being lost on amend

[Mateusz Kwapich]

# HG changeset patch
# User Mateusz Kwapich <mitrandir at fb.com>
# Date 1463693722 25200
#      Thu May 19 14:35:22 2016 -0700
# Node ID ccd61c869f63297fbae2662314afcb7b3dce5224
# Parent  f00f1de16454dfd31ee5e3fe301ab3225df76698
localrepo: prevent executable-bit only changes from being lost on amend

If you have just executable-bit change and amend it twice it will vanish:

 * After the first amend the commit will have the proper executable bit set
   in manifest but it won't have the the file on the list of files in
   changelog.

 * The second amend will read the wrong list of files from changelog and it
   will copy the manifest entry from parent for this file.

 * Voila! The change is lost.

This change repairs the bug in localrepo causing this and adds a test for it.

diff --git a/mercurial/localrepo.py b/mercurial/localrepo.py
--- a/mercurial/localrepo.py
+++ b/mercurial/localrepo.py
@@ -1397,6 +1397,8 @@ class localrepository(object):
             node = fctx.filenode()
             if node in [fparent1, fparent2]:
                 self.ui.debug('reusing %s filelog entry\n' % fname)
+                if manifest1.flags(fname) != fctx.flags():
+                    changelist.append(fname)
                 return node
 
         flog = self.file(fname)
diff --git a/tests/test-commit-amend.t b/tests/test-commit-amend.t
--- a/tests/test-commit-amend.t
+++ b/tests/test-commit-amend.t
@@ -1156,3 +1156,21 @@ directory)
      rev    offset  length  delta linkrev nodeid       p1           p2
        0         0      88     -1       3 34a4d536c0c0 000000000000 000000000000
 
+Test if amend preserves executable bit changes
+  $ chmod +x newdirname/commonfile.py
+  $ hg ci -m chmod
+  $ hg ci --amend -m "chmod amended"
+  $ hg ci --amend -m "chmod amended second time"
+  $ hg log -p --git -r .
+  changeset:   8:b1326f52dddf
+  branch:      newdirname
+  tag:         tip
+  parent:      5:7fd235f7cb2f
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     chmod amended second time
+  
+  diff --git a/newdirname/commonfile.py b/newdirname/commonfile.py
+  old mode 100644
+  new mode 100755
+