$ git clone -n https://src.fedoraproject.org/rpms/btrfs-progs.git /var/lib/mock/f39-build-1530740-36198/root/chroot_tmpdir/scmroot/btrfs-progs
Cloning into '/var/lib/mock/f39-build-1530740-36198/root/chroot_tmpdir/scmroot/btrfs-progs'...
$ git fetch origin 79b7d24868cc5e79d1e62849aa53cb92c304eb81:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/btrfs-progs
 * [new ref]         79b7d24868cc5e79d1e62849aa53cb92c304eb81 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 79b7d24 Update to 6.5.1