$ git clone -n https://github.com/xcp-ng-rpms/expat.git /var/lib/mock/v8.3-u-gln1-10995-29431/root/chroot_tmpdir/scmroot/expat
Cloning into '/var/lib/mock/v8.3-u-gln1-10995-29431/root/chroot_tmpdir/scmroot/expat'...
$ git fetch origin f7c8675e9e6c4485af6b223707335c2de2a91eb1:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/expat
 * [new ref]         f7c8675e9e6c4485af6b223707335c2de2a91eb1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f7c8675 bump release for test build