How can I tell if anything was fetched?

I have a cron job that regularly fetches into a bare repo. Currently, the job then pushes the repo to another remote, regardless of whether or not anything was actually fetched. That's a waste.

What is the best way to know whether or not anything was received during the fetch? I don't want to be stuck trying to parse the answer out of STDOUT and STDERR...

One approach might be to first generate a state-of-the-repo SHA1:
    # http://stackoverflow.com/a/7350019/834039
    # http://git-scm.com/book/ch9-2.html
    {
        git rev-list --objects --all
        git rev-list --objects -g --no-walk --all
        git rev-list --objects --no-walk \
            $(git fsck --unreachable |
              grep '^unreachable commit' |
              cut -d' ' -f3)
    } | sort | uniq | git hash-object -w --stdin

I could then do the git fetch, generate another state-of-the-repo SHA1 and compare...

Thoughts?

-- Phil Lawrence