$ git clone -n https://src.fedoraproject.org/rpms/rust-cfg-expr.git /var/lib/mock/f45-build-40727-775/root/chroot_tmpdir/scmroot/rust-cfg-expr
Cloning into '/var/lib/mock/f45-build-40727-775/root/chroot_tmpdir/scmroot/rust-cfg-expr'...
$ git fetch origin b6ed302267aa7ba2b359500b56ea1c58af2a2f92:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-cfg-expr
 * [new ref]         b6ed302267aa7ba2b359500b56ea1c58af2a2f92 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b6ed302 Update to version 0.20.9; Fixes RHBZ#2521272