$ git clone -n https://src.fedoraproject.org/rpms/diffoscope.git /var/lib/mock/f41-build-832307-14884/root/chroot_tmpdir/scmroot/diffoscope
Cloning into '/var/lib/mock/f41-build-832307-14884/root/chroot_tmpdir/scmroot/diffoscope'...
$ git fetch origin aa19fa5217307f168069037e839fa15eaab76c3f:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/diffoscope
 * [new ref]         aa19fa5217307f168069037e839fa15eaab76c3f -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at aa19fa5 Version 264