gitlog: implement __iter__ on changelog

This allows `hg phase --force --draft -r .` to work, for example.

Differential Revision: https://phab.mercurial-scm.org/D8264

hgext/git/gitlog.py

@@ -103,6 +103,9 b' class changelog(baselog):'
         except error.LookupError:
             return False
 
+    def __iter__(self):
+        return iter(pycompat.xrange(len(self)))
+
     @property
     def filteredrevs(self):
         # TODO: we should probably add a refs/hg/ namespace for hidden