rebase: sort roots by revision

Previously we were sorting them by whatever implicit sort order we got
between changectx instances. Sorting by rev at least makes some sense,
so I chose that.

Differential Revision: https://phab.mercurial-scm.org/D2301

hgext/rebase.py

@@ -1650,7 +1650,9 b' def buildstate(repo, destmap, collapse):'
     roots = list(repo.set('roots(%ld)', sortedsrc[0]))
     if not roots:
         raise error.Abort(_('no matching revisions'))
-    roots.sort()
+    def revof(r):
+        return r.rev()
+    roots = sorted(roots, key=revof)
     state = dict.fromkeys(rebaseset, revtodo)
     emptyrebase = (len(sortedsrc) == 1)
     for root in roots: