$ git clone -n https://src.fedoraproject.org/rpms/btrfs-progs.git /var/lib/mock/f40-build-798239-141768/root/chroot_tmpdir/scmroot/btrfs-progs
Cloning into '/var/lib/mock/f40-build-798239-141768/root/chroot_tmpdir/scmroot/btrfs-progs'...
$ git fetch origin be60cd2958e75a7a33564d173a182619874b4e36:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/btrfs-progs
 * [new ref]         be60cd2958e75a7a33564d173a182619874b4e36 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at be60cd2 Update to 6.7.1