merge: fix bug going backwards for already reverted files (issue1303)

mercurial/merge.py

@@ -185,8 +185,9 b' def manifestmerge(repo, p1, p2, pa, over'
                 if overwrite:
                     act("clobbering", "g", f, rflags)
                 # or are we going back in time and clean?
-                elif backwards and not n[20:]:
-                    act("reverting", "g", f, rflags)
+                elif backwards:
+                    if not n[20:] or not p2[f].cmp(p1[f].data()):
+                        act("reverting", "g", f, rflags)
                 # are both different from the ancestor?
                 elif n != a and m2[f] != a:
                     act("versions differ", "m", f, f, f, rflags, False)

tests/test-execute-bit.out

@@ -3,6 +3,6 b' 79abf14474dc tip'
 % make sure we notice the change of mode if the cached size == -1
 n   0         -1 unset               a
 M a
-0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+1 files updated, 0 files merged, 0 files removed, 0 files unresolved
 d69afc33ff8a
 not executable -- whew