$ git clone -n https://github.com/xcp-ng-rpms/expat.git /var/lib/mock/v8.3-u-gln1-10991-29430/root/chroot_tmpdir/scmroot/expat
Cloning into '/var/lib/mock/v8.3-u-gln1-10991-29430/root/chroot_tmpdir/scmroot/expat'...
$ git fetch origin de6f9b76853491e4d99632f5787e969641245236:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/expat
 * [new ref]         de6f9b76853491e4d99632f5787e969641245236 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at de6f9b7 bump release for test build