$ git clone -n https://github.com/xcp-ng-rpms/python /var/lib/mock/v8.3-incoming-10645-29199/root/chroot_tmpdir/scmroot/python
Cloning into '/var/lib/mock/v8.3-incoming-10645-29199/root/chroot_tmpdir/scmroot/python'...
$ git fetch origin 3f566a3c78fc263c649b939ea870d8d8460219a1:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/python
 * [new ref]         3f566a3c78fc263c649b939ea870d8d8460219a1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3f566a3 Merge pull request #1 from xcp-ng-rpms/8.3-XS-1557