Pitfalls in auto-fast-forwarding heads that are not checked out?

I am building a small git wrapper around puppet, and one of the actions it performs is auto-fastforwarding of branches without checking them out.

In simplified code... we ensure that we are on a head called master, and in some cases "ppg commit", will commit to master and...

  ## early on
  # sanity-check we are on master
  headname=$(git rev-parse --symbolic-full-name --revs-only HEAD)
  if [ "$headname" -ne "refs/heads/headname" ]; then
      echo >&2 "ERROR: can only issue --immediate commit from the
master branch!"
      exit 1
  fi

  ## then
  git commit -bla blarg baz

  ## and then...

  # ensure we can ff
  head_sha1=$(git rev-parse --revs-only master)
  mb=$(git merge-base $production_sha1 refs/heads/master)
  if [[ "$mb" -ne "$production_sha1" ]]; then
      echo >&2 "ERROR: cannot fast-forward master to production"
      exit 1
  fi
  $GIT_EXEC_PATH/git-update-ref -m "ppg immediate commit"
refs/heads/production $head_sha1 $production_sha1 || exit 1

Are there major pitfalls in this approach? I cannot think of any, but git has stayed away from updating my local tracking branches; so maybe there's a reason for that...

cheers,

m
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 martin.langhoff@gmail.com
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