$ git clone -n https://src.fedoraproject.org/rpms/btrfs-progs.git /var/lib/mock/f41-build-850511-165462/root/chroot_tmpdir/scmroot/btrfs-progs
Cloning into '/var/lib/mock/f41-build-850511-165462/root/chroot_tmpdir/scmroot/btrfs-progs'...
$ git fetch origin 8b8d89fdeef10351861bf3de6af63e25a35cb8ec:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/btrfs-progs
 * [new ref]         8b8d89fdeef10351861bf3de6af63e25a35cb8ec -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8b8d89f Update to 6.11