$ git clone -n https://src.fedoraproject.org/rpms/diffoscope.git /var/lib/mock/f39-build-1689290-41127/root/chroot_tmpdir/scmroot/diffoscope
Cloning into '/var/lib/mock/f39-build-1689290-41127/root/chroot_tmpdir/scmroot/diffoscope'...
$ git fetch origin 0c87945f1813baa250e53cb7b4db3e9f4224a362:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/diffoscope
 * [new ref]         0c87945f1813baa250e53cb7b4db3e9f4224a362 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 0c87945 Upload sources