$ git clone -n https://src.fedoraproject.org/rpms/rust-chrono /var/lib/mock/f42-build-3433516-45428/root/chroot_tmpdir/scmroot/rust-chrono
Cloning into '/var/lib/mock/f42-build-3433516-45428/root/chroot_tmpdir/scmroot/rust-chrono'...
$ git fetch origin fb42f640fbcf5acc9397c7762eb16a0778e70c1e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-chrono
 * [new ref]         fb42f640fbcf5acc9397c7762eb16a0778e70c1e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fb42f64 Update to version 0.4.40; Fixes RHBZ#2348377