$ git clone -n https://src.fedoraproject.org/rpms/gprbuild.git /var/lib/mock/f40-build-802430-144012/root/chroot_tmpdir/scmroot/gprbuild
Cloning into '/var/lib/mock/f40-build-802430-144012/root/chroot_tmpdir/scmroot/gprbuild'...
$ git fetch origin 20458ffac9831f377fb1e30cb68814458ddb658b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gprbuild
 * [new ref]         20458ffac9831f377fb1e30cb68814458ddb658b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 20458ff one more comment