Metalsmith's documentation does not explain much about the path() function: #path(paths...): Resolve any amount of paths... relative to the working directory. This is useful for plugins who want to read extra assets from another directory, for example ./templates. That's it. That's the sum total of the documentation.
What arguments are expected and what do they do?
What I want to do is: Process different source directories according to different Metalsmith plugins. This seems to require me to create multiple templates/ directories under the separate source directories. If I want metalsmith-templates to look for templates under ../templates rather than ./templates, I would assume path() can do that... but in the absence of any meaningful documentation, I have no way to anticipate how to do it, or even whether it will work at all (short of reading the source code).