$ git clone -n https://src.fedoraproject.org/rpms/mutter.git /var/lib/mock/f42-build-side-1-3587348-46930/root/chroot_tmpdir/scmroot/mutter
Cloning into '/var/lib/mock/f42-build-side-1-3587348-46930/root/chroot_tmpdir/scmroot/mutter'...
$ git fetch origin 8279e6f3b4e6e0cc0f9dc1dc674efbef0674a7d2:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mutter
 * [new ref]         8279e6f3b4e6e0cc0f9dc1dc674efbef0674a7d2 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8279e6f Update to 48.4