$ git clone -n https://src.fedoraproject.org/rpms/mp3gain.git /var/lib/mock/f45-build-19190-543/root/chroot_tmpdir/scmroot/mp3gain
Cloning into '/var/lib/mock/f45-build-19190-543/root/chroot_tmpdir/scmroot/mp3gain'...
$ git fetch origin 81aa3d14330937884c5fc9f378166d07e33393c0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mp3gain
 * [new ref]         81aa3d14330937884c5fc9f378166d07e33393c0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 81aa3d1 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild