merge: allow merging going backwards New behavior is generally superior and more correct, except possibly with regards to missing files. hg up . is now effectively a no-op, which is probably the desired behavior for people expecting to move to tip, but may surprise people who were expecting deleted files to reappear. case 1: update to . a-w -> a-w classic: ancestor a missing recreated right? rmed recreated WRONG added forgotten WRONG changed preserved RIGHT conflicted can't happen backward merge: ancestor a (NO EFFECT) missing missing wrong? rm'ed rm'ed RIGHT added preserved RIGHT changed preserved RIGHT conflicted can't happen case 2: update to ancestor of . a-b-w -> b-w \ a classic: ancestor a missing recreated right? rmed recreated wrong? added forgotten wrong? changed preserved RIGHT conflicted preserved wrong? backwards merge: ancestor b missing missing or conflict right? rm'ed missing or conflict right? changed preserved RIGHT conflicted merge RIGHT added preserved right?

--- a/mercurial/merge.py	Mon Jun 08 18:14:44 2009 -0500
+++ b/mercurial/merge.py	Mon Jun 08 18:14:44 2009 -0500
@@ -131,11 +131,14 @@
 
     m1 = p1.manifest()
     m2 = p2.manifest()
-    ma = pa.manifest()
     backwards = (pa == p2)
 
-    if backwards or overwrite:
+    if overwrite:
         ma = m1
+    elif backwards:
+        ma = p1.p1().manifest()
+    else:
+        ma = pa.manifest()
 
     action = []
     copy, copied, diverge = {}, {}, {}