$ git clone -n https://src.fedoraproject.org/rpms/libarrow.git /var/lib/mock/f40-build-1951148-25188/root/chroot_tmpdir/scmroot/libarrow
Cloning into '/var/lib/mock/f40-build-1951148-25188/root/chroot_tmpdir/scmroot/libarrow'...
$ git fetch origin 6d1518363e121ac64c4997ec73076c18c02d91e6:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/libarrow
 * [new ref]         6d1518363e121ac64c4997ec73076c18c02d91e6 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6d15183 rebuild with liborc-1.9.4