add a fix for issue 1175

If we copy a file followed by an update, it's possible for the parent
manifest to no longer contain the source file of the copy, which could cause
commit to fail. If this happens, we search backwares from the first
parent to find the most likely original revision.

tests/test-issue1175

@@ -0,0 +1,20 b''
+#!/bin/sh
+rm -rf a
+hg init a
+cd a
+touch a
+hg ci -Am0
+hg mv a a1
+hg ci -m1
+hg co 0
+hg mv a a2
+hg up
+hg ci -m2
+
+touch a
+hg ci -Am3
+hg mv a b
+hg ci -Am4 a
+hg ci --debug --traceback -Am5 b
+hg verify
+hg export --git tip

tests/test-issue1175.out

@@ -0,0 +1,24 b''
+adding a
+1 files updated, 0 files merged, 1 files removed, 0 files unresolved
+warning: detected divergent renames of a to:
+ a2
+ a1
+1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+adding a
+b
+ b: searching for copy revision for a
+ b: copy a:b80de5d138758541c5f05265ad144ab9fa86d1db
+checking changesets
+checking manifests
+crosschecking files in changesets and manifests
+checking files
+4 files, 6 changesets, 4 total revisions
+# HG changeset patch
+# User test
+# Date 0 0
+# Node ID 755e75751bf67eb4378bca61987df035d90a7a06
+# Parent  7399822c2e395fe7d57c2fcf4b310f6fb22f8c2d
+5
+
+diff --git a/b b/b
+new file mode 100644

mercurial/localrepo.py

@@ -708,7 +708,7 b' class localrepository(repo.repository):'
             #    \- 2 --- 4        as the merge base
             #
 
-            cr = manifest1.get(cf, nullid)
+            cr = manifest1.get(cf)
             nfp = fp2
 
             if manifest2: # branch merge
@@ -717,6 +717,24 b' class localrepository(repo.repository):'
                         cr = manifest2[cf]
                         nfp = fp1
 
+            # find source in nearest ancestor if we've lost track
+            if not cr:
+                self.ui.debug(_(" %s: searching for copy revision for %s\n") %
+                              (fn, cf))
+                p1 = self.dirstate.parents()[0]
+                rev = self.changelog.rev(p1)
+                seen = {-1:None}
+                visit = [rev]
+                while visit:
+                    for p in self.changelog.parentrevs(visit.pop(0)):
+                        if p not in seen:
+                            seen[p] = True
+                            visit.append(p)
+                            ctx = self.changectx(p)
+                            if cf in ctx:
+                                cr = ctx[cf].filenode()
+                                break
+
             self.ui.debug(_(" %s: copy %s:%s\n") % (fn, cf, hex(cr)))
             meta["copy"] = cf
             meta["copyrev"] = hex(cr)