$ git clone -n https://gitee.com/opencloudos-stream/tumbler.git /var/lib/mock/dist-oc9-epol-build-106913-66924/root/chroot_tmpdir/scmroot/tumbler
Cloning into '/var/lib/mock/dist-oc9-epol-build-106913-66924/root/chroot_tmpdir/scmroot/tumbler'...
$ git fetch origin master:KOJI_FETCH_HEAD
From https://gitee.com/opencloudos-stream/tumbler
 * [new branch]      master     -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at a0fa191 update