$ git clone -n https://src.fedoraproject.org/rpms/rust-cargo.git /var/lib/mock/f42-build-side-1-3585861-46908/root/chroot_tmpdir/scmroot/rust-cargo
Cloning into '/var/lib/mock/f42-build-side-1-3585861-46908/root/chroot_tmpdir/scmroot/rust-cargo'...
$ git fetch origin 841e197c54b98d60d1654ce28731cdd558e05a19:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-cargo
 * [new ref]         841e197c54b98d60d1654ce28731cdd558e05a19 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 841e197 Update to version 0.87.1; Fixes RHBZ#2357164