$ git clone -n https://src.fedoraproject.org/rpms/xpra.git /var/lib/mock/f39-build-1744955-41397/root/chroot_tmpdir/scmroot/xpra
Cloning into '/var/lib/mock/f39-build-1744955-41397/root/chroot_tmpdir/scmroot/xpra'...
$ git fetch origin c76677cdd35ed8d481ecc8b1402e7cd1211c9ce1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/xpra
 * [new ref]         c76677cdd35ed8d481ecc8b1402e7cd1211c9ce1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c76677c Move ffmpeg plugin to Fedora