$ git clone -n https://src.fedoraproject.org/rpms/rust-matrixmultiply.git /var/lib/mock/f45-build-43148-800/root/chroot_tmpdir/scmroot/rust-matrixmultiply
Cloning into '/var/lib/mock/f45-build-43148-800/root/chroot_tmpdir/scmroot/rust-matrixmultiply'...
$ git fetch origin 44029452c5837b058aa19724818ebf4c0cd7041f:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-matrixmultiply
 * [new ref]         44029452c5837b058aa19724818ebf4c0cd7041f -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4402945 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild