$ git clone -n https://src.fedoraproject.org/rpms/arbor.git /var/lib/mock/f39-build-1893685-42802/root/chroot_tmpdir/scmroot/arbor
Cloning into '/var/lib/mock/f39-build-1893685-42802/root/chroot_tmpdir/scmroot/arbor'...
$ git fetch origin 06e1cefc66d04a814071e6fc985972a255d80c23:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/arbor
 * [new ref]         06e1cefc66d04a814071e6fc985972a255d80c23 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 06e1cef Do not enable extra ISA extensions based on the build host