$ git clone -n https://src.fedoraproject.org/rpms/rubygem-rgen.git /var/lib/mock/f39-build-1470841-33922/root/chroot_tmpdir/scmroot/rubygem-rgen
Cloning into '/var/lib/mock/f39-build-1470841-33922/root/chroot_tmpdir/scmroot/rubygem-rgen'...
$ git fetch origin 0b7a0ec4e0f35a05e1a5e81ed2e243ca22ad2a75:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-rgen
 * [new ref]         0b7a0ec4e0f35a05e1a5e81ed2e243ca22ad2a75 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 0b7a0ec Rebuilt for https://fedoraproject.org/wiki/Fedora_39_Mass_Rebuild