$ git clone -n https://src.fedoraproject.org/rpms/rubygem-bindex.git /var/lib/mock/f40-build-2033535-47813/root/chroot_tmpdir/scmroot/rubygem-bindex
Cloning into '/var/lib/mock/f40-build-2033535-47813/root/chroot_tmpdir/scmroot/rubygem-bindex'...
$ git fetch origin 5e2d3af3d1ccd119b2666abaae120d82089d30a5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-bindex
 * [new ref]         5e2d3af3d1ccd119b2666abaae120d82089d30a5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 5e2d3af Fix FTBFS due to Minitest 5.19+ incompatibility.