$ git clone -n https://src.fedoraproject.org/rpms/rust-gtk-sys /var/lib/mock/f42-build-3429024-45391/root/chroot_tmpdir/scmroot/rust-gtk-sys
Cloning into '/var/lib/mock/f42-build-3429024-45391/root/chroot_tmpdir/scmroot/rust-gtk-sys'...
$ git fetch origin d54b707f5063a8c36c71e88806b12efd6e9a9bd5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-gtk-sys
 * [new ref]         d54b707f5063a8c36c71e88806b12efd6e9a9bd5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at d54b707 Update to version 0.18.2; Fixes RHBZ#2331133