Restore backwards compatibility

When status indicators were added, backwards compatibility was unnecessarily
broken. This makes things like looking at old non-rebased branches, or running
git bisect, unnecessarily annoying. This change adds an is_callable to restore
backwards compatibility and removes the version check that was added in response
to this break.

Change-Id: Ia05aa73a1b027e667c52f54b6d6fdf6f42bbbadf