$ git clone -n https://src.fedoraproject.org/forks/tstellar/rpms/llvm.git /var/lib/mock/f43-build-59107338-6571137/root/chroot_tmpdir/scmroot/llvm
Cloning into '/var/lib/mock/f43-build-59107338-6571137/root/chroot_tmpdir/scmroot/llvm'...
$ git fetch origin f18b07512d81870fafae92cc0388c9aa19696bf3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/forks/tstellar/rpms/llvm
 * [new ref]         f18b07512d81870fafae92cc0388c9aa19696bf3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f18b075 Fix build with glibc >= 2.42