$ git clone -n https://src.fedoraproject.org/rpms/ImageMagick.git /var/lib/mock/f42-build-868858-176294/root/chroot_tmpdir/scmroot/ImageMagick
Cloning into '/var/lib/mock/f42-build-868858-176294/root/chroot_tmpdir/scmroot/ImageMagick'...
$ git fetch origin 26aa40f4e74801808b3b58596ded6b9cd5cbe833:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ImageMagick
 * [new ref]         26aa40f4e74801808b3b58596ded6b9cd5cbe833 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 26aa40f Rebuild on side-tag