Previous patches add a safe mode for sharing repositories which involve sharing
of source requirements and config files.
In certain situations we might need to add a config to source repository which
we does not want to share. For this, we add a .hg/hgrc-not-shared which won't
be shared.
This also adds a --non-shared flag to hg config command to see the
non-shared config.
Why this limitation ? Can't a share have this file too ?