$ git clone -n https://src.fedoraproject.org/rpms/rust-matrixmultiply.git /var/lib/mock/f39-build-1493946-34542/root/chroot_tmpdir/scmroot/rust-matrixmultiply
Cloning into '/var/lib/mock/f39-build-1493946-34542/root/chroot_tmpdir/scmroot/rust-matrixmultiply'...
$ git fetch origin 0bcede19fb75a2054162e889483223558cf07764:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-matrixmultiply
 * [new ref]         0bcede19fb75a2054162e889483223558cf07764 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 0bcede1 Update to version 0.3.8; Fixes RHBZ#2240007