`ent edit ${ISSUE}` with no change fails

After the user closes the editor, ent blindly tries to commit, which
fails like this:
```
stdout: On branch entomologist-data
nothing to commit, working tree clean

stderr:
Error: Failed to run git

Caused by:
    Oops, something went wrong
```

Probably we should run `git status` after the editor finishes, to see
if there's anything to commit.