$ git clone -n https://src.fedoraproject.org/rpms/stgit.git /var/lib/mock/f42-build-3273257-41310/root/chroot_tmpdir/scmroot/stgit
Cloning into '/var/lib/mock/f42-build-3273257-41310/root/chroot_tmpdir/scmroot/stgit'...
$ git fetch origin 59625fb77d057bab1dd4aa284aba5d7834648536:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/stgit
 * [new ref]         59625fb77d057bab1dd4aa284aba5d7834648536 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 59625fb Update to version 2.5.1 (rhbz#2332427)