$ git clone -n https://src.fedoraproject.org/rpms/rust-clang-sys.git /var/lib/mock/f39-build-2250656-54034/root/chroot_tmpdir/scmroot/rust-clang-sys
Cloning into '/var/lib/mock/f39-build-2250656-54034/root/chroot_tmpdir/scmroot/rust-clang-sys'...
$ git fetch origin b4859a3af6d47e50089e1d2ec2f8da6164e58b16:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-clang-sys
 * [new ref]         b4859a3af6d47e50089e1d2ec2f8da6164e58b16 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b4859a3 Update to version 1.7.0; Fixes RHBZ#2256353