$ git clone -n https://src.fedoraproject.org/rpms/mock.git /var/lib/mock/f39-build-2083632-49951/root/chroot_tmpdir/scmroot/mock
Cloning into '/var/lib/mock/f39-build-2083632-49951/root/chroot_tmpdir/scmroot/mock'...
$ git fetch origin c29f6c17bc0da49044471ec533974692f5fbe62f:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mock
 * [new ref]         c29f6c17bc0da49044471ec533974692f5fbe62f -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c29f6c1 Update mock to 5.3-1