$ git clone -n https://src.fedoraproject.org/rpms/rubygem-childprocess.git /var/lib/mock/f45-build-34817-691/root/chroot_tmpdir/scmroot/rubygem-childprocess
Cloning into '/var/lib/mock/f45-build-34817-691/root/chroot_tmpdir/scmroot/rubygem-childprocess'...
$ git fetch origin da9c7fc5444a753642988b0eb86b8f3581e4307a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-childprocess
 * [new ref]         da9c7fc5444a753642988b0eb86b8f3581e4307a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at da9c7fc Update to childprocess 5.1.0.