omitting repo headers with 'mr run'

[Adam Spiers]

Hi all,

I have just coded git-wip[1], a little utility which returns true if
the current repo has any work in progress, i.e. commits out of sync
with upstream, or unmodified/untracked files.

I would like to run this across all my repositories via `mr wip', so I
wrote the following mr action:

    git_wip =
        if git wip; then
            git branch -v -v
            git status -s
        fi

However, if I have (say) 70 repositories and only two of them have
work in progress, `mr wip' outputs about 150 lines, of which only 10
lines are useful.  This is because for every repository it outputs
a header line like:

    mr wip: ~/.GIT/adamspiers.org/mutt

plus a blank line.  Is there any existing way I can make it only
output the repositories for which the git_wip action generates some
output?  If not, I'm happy to submit a patch but would welcome
feedback on the best approach; adding a new command-line option
similar to --quiet perhaps?

Thanks,
Adam

[1] https://github.com/aspiers/git-config#readme