$ git clone -n https://src.fedoraproject.org/rpms/python-flufl-bounce.git /var/lib/mock/f39-build-1615718-38639/root/chroot_tmpdir/scmroot/python-flufl-bounce
Cloning into '/var/lib/mock/f39-build-1615718-38639/root/chroot_tmpdir/scmroot/python-flufl-bounce'...
$ git fetch origin ddba00e79b762961878c2f03a7d4b993596411b1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/python-flufl-bounce
 * [new ref]         ddba00e79b762961878c2f03a7d4b993596411b1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at ddba00e Update to 4.0