$ git clone -n https://src.fedoraproject.org/rpms/rust-cfg-expr.git /var/lib/mock/f40-build-2081289-49752/root/chroot_tmpdir/scmroot/rust-cfg-expr
Cloning into '/var/lib/mock/f40-build-2081289-49752/root/chroot_tmpdir/scmroot/rust-cfg-expr'...
$ git fetch origin dca610231624072b9b4f105281034e2b39e30845:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-cfg-expr
 * [new ref]         dca610231624072b9b4f105281034e2b39e30845 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at dca6102 Update to version 0.15.5; Fixes RHBZ#2238016