$ git clone -n https://src.fedoraproject.org/rpms/CImg.git /var/lib/mock/f42-build-3458757-45513/root/chroot_tmpdir/scmroot/CImg
Cloning into '/var/lib/mock/f42-build-3458757-45513/root/chroot_tmpdir/scmroot/CImg'...
$ git fetch origin 78b4b6b2a05454d746d178dc30e112030a2ff047:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/CImg
 * [new ref]         78b4b6b2a05454d746d178dc30e112030a2ff047 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 78b4b6b bump version