$ git clone -n https://src.fedoraproject.org/rpms/plymouth-kcm.git /var/lib/mock/f42-build-side-1-3578421-46814/root/chroot_tmpdir/scmroot/plymouth-kcm
Cloning into '/var/lib/mock/f42-build-side-1-3578421-46814/root/chroot_tmpdir/scmroot/plymouth-kcm'...
$ git fetch origin c4cc5567d9ffe8beaed09651b481f623ec030fa8:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/plymouth-kcm
 * [new ref]         c4cc5567d9ffe8beaed09651b481f623ec030fa8 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c4cc556 6.4.1