$ git clone -n https://src.fedoraproject.org/rpms/rubygem-rmagick.git /var/lib/mock/f40-build-733994-105646/root/chroot_tmpdir/scmroot/rubygem-rmagick
Cloning into '/var/lib/mock/f40-build-733994-105646/root/chroot_tmpdir/scmroot/rubygem-rmagick'...
$ git fetch origin 86d04085ad4d5211f1f39b0b71a63fdec8a6cb22:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-rmagick
 * [new ref]         86d04085ad4d5211f1f39b0b71a63fdec8a6cb22 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 86d0408 5.3.0