I've come up with a tag (per-directory-settings) for questions about configuration files that override or merge over one another based on an answer to this question if you think the name of it sucks, please come up with a better one; and tag anything you think this may apply to.
Off the top of my head I can think of
.gitignore, and Apache2 .htaccess. If you come up with other ones please tag them accordingly.
The tag is needed because the concept exists in so many different pieces of software (git, apache2, vim, emacs). People could figure out if a piece of software supports such a functionality just by looking at the tag on a relevant question. Or by filtering question on both the name of the software and the tag I'm proposing