$ git clone -n https://src.fedoraproject.org/rpms/btrfs-fuse.git /var/lib/mock/f40-build-763251-122453/root/chroot_tmpdir/scmroot/btrfs-fuse
Cloning into '/var/lib/mock/f40-build-763251-122453/root/chroot_tmpdir/scmroot/btrfs-fuse'...
$ git fetch origin 8844151622ec1cfca44207dd6282b39ed1c09854:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/btrfs-fuse
 * [new ref]         8844151622ec1cfca44207dd6282b39ed1c09854 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8844151 Update to git snapshot 812c4b7