$ git clone -n https://src.fedoraproject.org/rpms/rust-jxl-vardct.git /var/lib/mock/f39-build-1786130-41711/root/chroot_tmpdir/scmroot/rust-jxl-vardct
Cloning into '/var/lib/mock/f39-build-1786130-41711/root/chroot_tmpdir/scmroot/rust-jxl-vardct'...
$ git fetch origin 38138cc842f7b9e89dda56d473abd47f0998e508:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-jxl-vardct
 * [new ref]         38138cc842f7b9e89dda56d473abd47f0998e508 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 38138cc Initial Fedora packaging (rhbz#2248923)