Re: git push to a non-bare repository

"Shawn O. Pearce" [off-list ref] writes:

  git-diff $old $new | git-apply --index ?

If the patch does not apply, nothing gets updated.  If it does apply,
the index is also updated and stat data updated.

And if you are only checking then perhaps instead of --index
use --check, so that the actual updates are deferred?