$ git clone -n https://src.fedoraproject.org/rpms/rust-coreos-installer.git /var/lib/mock/f40-build-2054033-49096/root/chroot_tmpdir/scmroot/rust-coreos-installer
Cloning into '/var/lib/mock/f40-build-2054033-49096/root/chroot_tmpdir/scmroot/rust-coreos-installer'...
$ git fetch origin ce3f7762ddc5eb5c688a5f01a3c5b98e9b3b25a8:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-coreos-installer
 * [new ref]         ce3f7762ddc5eb5c688a5f01a3c5b98e9b3b25a8 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at ce3f776 Replace rdcore patch with %prep work