$ git clone -n https://src.fedoraproject.org/rpms/diffoscope.git /var/lib/mock/f39-build-2432936-60579/root/chroot_tmpdir/scmroot/diffoscope
Cloning into '/var/lib/mock/f39-build-2432936-60579/root/chroot_tmpdir/scmroot/diffoscope'...
$ git fetch origin 5fafb4fbea0967065034ac56aad58a09defc8fd0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/diffoscope
 * [new ref]         5fafb4fbea0967065034ac56aad58a09defc8fd0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 5fafb4f Version 257