Merge user and project level config files?

[mrlacey]

How should the specification of project and user level config files be handled?

The current behavior is that a user level config file is only used if a project level one isn't defined.
However, if both are defined, if may be desirable to use the settings from both files.

For example, if a user file may contain lots of rules but a project only contains one (or a few) then the user would lose all the benefit from the effort they've put in to customizing their environment.

Merging the two config files, if they're both defined, seems the most appropriate action, but consideration must be given to potential conflicts between the two files.

Some investigation is required to see if this can work for all scenarios and what the exact rules around merging should be.