Fix copy detection corner case

We were aborting if the copied from rev was before the cut-off limit,
rather than the copied _to_ rev. The copied from rev can be
arbitrarily old.

mercurial/merge.py

@@ -109,10 +109,10 b' def findcopies(repo, m1, m2, ma, limit):'
         visit = [fctx]
         while visit:
             fc = visit.pop()
+            if fc.path() != orig and fc.path() not in old:
+                old[fc.path()] = 1
             if fc.rev() < limit:
                 continue
-            if fc.path() != orig and fc.path() not in old:
-                old[fc.path()] = 1
             visit += fc.parents()
 
         old = old.keys()