$ git clone -n https://src.fedoraproject.org/rpms/rubygem-opengl.git /var/lib/mock/f42-build-865342-173025/root/chroot_tmpdir/scmroot/rubygem-opengl
Cloning into '/var/lib/mock/f42-build-865342-173025/root/chroot_tmpdir/scmroot/rubygem-opengl'...
$ git fetch origin b93a5b61b3459c60d4c770c00cced16a6cd8c745:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-opengl
 * [new ref]         b93a5b61b3459c60d4c770c00cced16a6cd8c745 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b93a5b6 kill bootstrap