$ git clone -n https://src.fedoraproject.org/rpms/nullmodem.git /var/lib/mock/f41-build-751272-13389/root/chroot_tmpdir/scmroot/nullmodem
Cloning into '/var/lib/mock/f41-build-751272-13389/root/chroot_tmpdir/scmroot/nullmodem'...
$ git fetch origin 3636c9a33b166c11012cf284621b22307aef6a93:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/nullmodem
 * [new ref]         3636c9a33b166c11012cf284621b22307aef6a93 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3636c9a Eliminate use of obsolete %patchN syntax (#2283636)