$ git clone -n https://github.com/xcp-ng-rpms/gmp /var/lib/mock/v8.3-u-pcoval1-11010-29444/root/chroot_tmpdir/scmroot/gmp
Cloning into '/var/lib/mock/v8.3-u-pcoval1-11010-29444/root/chroot_tmpdir/scmroot/gmp'...
$ git fetch origin 4f347dde728daae9d552edeee5e50c1206a7bafb:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/gmp
 * [new ref]         4f347dde728daae9d552edeee5e50c1206a7bafb -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4f347dd bump release for test build