$ git clone -n https://src.fedoraproject.org/rpms/rust-clang-sys.git /var/lib/mock/f45-build-40788-776/root/chroot_tmpdir/scmroot/rust-clang-sys
Cloning into '/var/lib/mock/f45-build-40788-776/root/chroot_tmpdir/scmroot/rust-clang-sys'...
$ git fetch origin 6c8c4c087c5c11fdf692d3541579e1bb286520d3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-clang-sys
 * [new ref]         6c8c4c087c5c11fdf692d3541579e1bb286520d3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6c8c4c0 Update to version 1.9.1; Fixes RHBZ#2520182