rebase: specify custom conflict marker labels for rebase (BC)

Changes rebase conflict markers to say 'source' and 'dest' instead of
'local' and 'other'.  This ends up looking like:

  one
  <<<<<<< dest:   a3e5c7fd master - bob: "A commit to master"
  master
  =======
  mine
  >>>>>>> source: c7fda3e5 - durham: "A commit to my feature branch"
  three

hgext/rebase.py

@@ -531,7 +531,8 b' def rebasenode(repo, rev, p1, state, col'
         repo.ui.debug("   detach base %d:%s\n" % (repo[base].rev(), repo[base]))
     # When collapsing in-place, the parent is the common ancestor, we
     # have to allow merging with it.
-    return merge.update(repo, rev, True, True, False, base, collapse)
+    return merge.update(repo, rev, True, True, False, base, collapse,
+                        labels=['dest', 'source'])
 
 def nearestrebased(repo, rev, state):
     """return the nearest ancestors of rev in the rebase result"""

tests/test-shelve.t

@@ -210,11 +210,11 b' ensure that we have a merge with unresol'
   +++ b/a/a
   @@ -1,2 +1,6 @@
    a
-  +<<<<<<< local: *  - shelve: "pending changes temporary commit" (glob)
+  +<<<<<<< dest: *  - shelve: "pending changes temporary commit" (glob)
    c
   +=======
   +a
-  +>>>>>>> other: * - shelve: "changes to '[mq]: second.patch'" (glob)
+  +>>>>>>> source: * - shelve: "changes to '[mq]: second.patch'" (glob)
   diff --git a/b.rename/b b/b.rename/b
   new file mode 100644
   --- /dev/null
@@ -604,11 +604,11 b' unshelve and conflicts with tracked and '
   M f
   ? f.orig
   $ cat f
-  <<<<<<< local: 5f6b880e719b  - shelve: "pending changes temporary commit"
+  <<<<<<< dest:   5f6b880e719b  - shelve: "pending changes temporary commit"
   g
   =======
   f
-  >>>>>>> other: 23b29cada8ba - shelve: "changes to 'commit stuff'"
+  >>>>>>> source: 23b29cada8ba - shelve: "changes to 'commit stuff'"
   $ cat f.orig
   g
   $ hg unshelve --abort
@@ -647,11 +647,11 b' unshelve and conflicts with tracked and '
   M f
   ? f.orig
   $ cat f
-  <<<<<<< local: 6b563750f973  - test: "intermediate other change"
+  <<<<<<< dest:   6b563750f973  - test: "intermediate other change"
   g
   =======
   f
-  >>>>>>> other: 23b29cada8ba - shelve: "changes to 'commit stuff'"
+  >>>>>>> source: 23b29cada8ba - shelve: "changes to 'commit stuff'"
   $ cat f.orig
   g
   $ hg unshelve --abort