match: enable 'subinclude:' syntax This adds a new rule syntax that allows the user to include a pattern file, but only have those patterns match against files underneath the subdirectory of the pattern file. This is useful when you have nested projects in a repository and the inner projects wants to set up ignore rules that won't affect other projects in the repository. It is also useful in high commit rate repositories for removing the root .hgignore as a point of contention.

copies: switch to using pathutil.dirname copies had it's own dirname implementation. Now that pathutils has a common one, let's use that instead.

pathutil: add dirname and join functions This adds dirname and join functions to pathutil which are explicitly for handling '/' delimited paths. The implementations are basically copy paste from python's posix os.path.dirname and os.path.join functions.