I tried to make an alias for committing several different git projects. I tried something like
cat projectPaths | \\
xargs -I project git --git-dir=project/.gi
If you have GNU Parallel http://www.gnu.org/software/parallel/ installed you should be able to do this:
cat projectPaths |
parallel -uj1 git --git-dir={}/.git --work-tree={} commit -a
In general this works too:
cat filelist | parallel -Xuj1 $EDITOR
in case you want to edit more than one file at a time (and you have set $EDITOR to your favorite editor).
-o for xargs (as mentioned elsewhere) only works for some versions of xargs (notably it does not work for GNU xargs).
Watch the intro video to learn more about GNU Parallel http://www.youtube.com/watch?v=OpaiGYxkSuQ