bundle2: only use callable return as reply handler When a bundle2 parts generator returns a non callable value, it should not be used as a reply handler. The changegroup part generator is already having this case of behavior when there is no changegroup to push. This changeset prevent a crash for user of the experimentable bundle2 feature.

resolve: report no argument warning using a hint With this change resolve and revert produce consistent output when run with no arguments: $ hg resolve abort: no files or directories specified (use --all to remerge all files) $ hg revert abort: no files or directories specified (use --all to revert all files)