arc's patch command is.. interesting in areas, and relies on arc. we should implement our own 'patch' command in moz-phab. more details to come, but it should accept a revision identifier or url, and provide options to apply the current diff to the corresponding local parent, to the currently active commit, or to head.

> to apply the current diff hg phabread also supports reading a whole stack of patches in one go.

Three workflows can be used by choosing arguments: - no argument - recreate commits from revisions - --nocommit - display diffs - --nocommit --apply - apply patches but do not commit - requires patch command If run with --force - patches are applied to the current commit. moved self.branch to the new `before_submit` function to allow the `patch` to work from the detached HEAD state.