$ git clone -n https://src.fedoraproject.org/rpms/v8-314.git /var/lib/mock/f40-build-780181-130701/root/chroot_tmpdir/scmroot/v8-314
Cloning into '/var/lib/mock/f40-build-780181-130701/root/chroot_tmpdir/scmroot/v8-314'...
$ git fetch origin 655ea1278103f9db9deebbff4665ff0ad78eab64:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/v8-314
 * [new ref]         655ea1278103f9db9deebbff4665ff0ad78eab64 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 655ea12 fix FTBFS by disabling -Werror, fix license tag, run away screaming