$ git clone -n https://src.fedoraproject.org/rpms/diffoscope.git /var/lib/mock/f42-build-3528285-46309/root/chroot_tmpdir/scmroot/diffoscope
Cloning into '/var/lib/mock/f42-build-3528285-46309/root/chroot_tmpdir/scmroot/diffoscope'...
$ git fetch origin 69dd956d78aadb38ca9595d9aa6ec5b821a095a5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/diffoscope
 * [new ref]         69dd956d78aadb38ca9595d9aa6ec5b821a095a5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 69dd956 Version 285