$ git clone -n https://src.fedoraproject.org/rpms/rust-cargo.git /var/lib/mock/f41-build-side-1-3133858-39704/root/chroot_tmpdir/scmroot/rust-cargo
Cloning into '/var/lib/mock/f41-build-side-1-3133858-39704/root/chroot_tmpdir/scmroot/rust-cargo'...
$ git fetch origin e47adfd8631c11fbad8af9cae3e08c940e9addf4:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-cargo
 * [new ref]         e47adfd8631c11fbad8af9cae3e08c940e9addf4 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e47adfd Bump git2, git2-curl, and libgit2-sys dependencies