flags: account for flag change when tracking rename relevant to merge

There are some logic filtering rename to the one relevant to the merge. That
logic was oblivious of flag change, leading to exec flag being dropped when
merged with a renamed.

There are two others bugs affecting this scenario. This patch fix the was where
there is not modification involved except for the flag change. Fixes for the
other bug are coming in later changesets.

Differential Revision: https://phab.mercurial-scm.org/D8531

mercurial/copies.py

@@ -534,9 +534,9 b' def _checksinglesidecopies('
         # thing in pathcopies(): pathcopies(x, y) can return a copy where the
         # destination doesn't exist in y.
         pass
-    elif m2[src] != mb[src]:
-        if not _related(c2[src], base[src]):
-            return
+    elif mb[src] != m2[src] and not _related(c2[src], base[src]):
+        return
+    elif mb[src] != m2[src] or mb.flags(src) != m2.flags(src):
         # modified on side 2
         for dst in dsts1:
             copy[dst] = src

tests/test-merge-exec.t

@@ -111,29 +111,25 b' make "a" renamed on the other side'
 merge them (from the rename side)
 
   $ hg merge 'desc("make a executable")'
-  1 files updated, 0 files merged, 0 files removed, 0 files unresolved (false !)
-  0 files updated, 0 files merged, 0 files removed, 0 files unresolved (true !)
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   (branch merge, don't forget to commit)
   $ hg st --copies
-  M z (false !)
-    a (false !)
+  M z
+    a
   $ [ -x z ] || echo "executable bit lost"
-  executable bit lost (true !)
 
 merge them (from the chmod side)
 
   $ hg up -C 'desc("make a executable")'
   1 files updated, 0 files merged, 1 files removed, 0 files unresolved
   $ hg merge 'desc("rename a to z")'
-  1 files updated, 0 files merged, 0 files removed, 0 files unresolved (false !)
-  1 files updated, 0 files merged, 1 files removed, 0 files unresolved (true !)
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   (branch merge, don't forget to commit)
   $ hg st --copies
   M z
-    a (false !)
+    a
   R a
   $ [ -x z ] || echo "executable bit lost"
-  executable bit lost (true !)
 
 
   $ cd ..