$ git clone -n https://src.fedoraproject.org/rpms/rust-rustc_version.git /var/lib/mock/f45-build-44560-815/root/chroot_tmpdir/scmroot/rust-rustc_version
Cloning into '/var/lib/mock/f45-build-44560-815/root/chroot_tmpdir/scmroot/rust-rustc_version'...
$ git fetch origin 9d3b6c6da28095866d609da15df0737eeadfcc01:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-rustc_version
 * [new ref]         9d3b6c6da28095866d609da15df0737eeadfcc01 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 9d3b6c6 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild