$ git clone -n https://src.fedoraproject.org/rpms/rust-cargo-readme.git /var/lib/mock/f40-build-2189926-51418/root/chroot_tmpdir/scmroot/rust-cargo-readme
Cloning into '/var/lib/mock/f40-build-2189926-51418/root/chroot_tmpdir/scmroot/rust-cargo-readme'...
$ git fetch origin 9192822b9ee43a7f09c5dc31e4736c0ee33bb3a3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-cargo-readme
 * [new ref]         9192822b9ee43a7f09c5dc31e4736c0ee33bb3a3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 9192822 Update to version 3.3.1; Fixes RHBZ#2248205