$ git clone -n https://src.fedoraproject.org/rpms/btrfs-assistant.git /var/lib/mock/f40-build-1944963-25179/root/chroot_tmpdir/scmroot/btrfs-assistant
Cloning into '/var/lib/mock/f40-build-1944963-25179/root/chroot_tmpdir/scmroot/btrfs-assistant'...
$ git fetch origin 1eef03f88b12100907e5be3b4021f5a71ab85e41:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/btrfs-assistant
 * [new ref]         1eef03f88b12100907e5be3b4021f5a71ab85e41 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1eef03f Update to 2.1.1 (fedora#2281564)