exchange: pass bundlecaps through to changegroup

The bundlecaps passed to exchange.getbundle were being dropped completely. We
should pass them on through to the changegroup.

This affected the remotefilelog extension, since it relies on those bundlecaps.

mercurial/exchange.py

@@ -596,7 +596,7 b' def getbundle(repo, source, heads=None, '
     """
     # build bundle here.
     cg = changegroup.getbundle(repo, source, heads=heads,
-                               common=common, bundlecaps=None)
+                               common=common, bundlecaps=bundlecaps)
     if bundlecaps is None or 'HG20' not in bundlecaps:
         return cg
     # very crude first implementation,