$ git clone -n https://src.fedoraproject.org/rpms/rust-blake3.git /var/lib/mock/f42-build-side-1-3499469-45965/root/chroot_tmpdir/scmroot/rust-blake3
Cloning into '/var/lib/mock/f42-build-side-1-3499469-45965/root/chroot_tmpdir/scmroot/rust-blake3'...
$ git fetch origin e7be98f3367aacd63db91b248af767e8a32153d3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-blake3
 * [new ref]         e7be98f3367aacd63db91b248af767e8a32153d3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e7be98f Update to version 1.8.1; fixes RHBZ#2353227