Working with multiple sources

I'd love for Jekyll to support multiple sources, like so:

```
source: ["docs", "dist"]
```

As it stands now our repo's contents in Bootstrap are quite messy as documentation is mixed with other various repo contents and it's hard to discern the organization of files. The example above highlights what I'd like to achieve: place our `.html` docs pages in a directory, keep the compiled CSS and JS files we generate and track via Git in `dist`, and then have Jekyll build from both those.

The current solution to this would be a build script or manually copy-pasta, but that sucks and puts the burden on others to solve. Given Jekyll already has the ability to specify contents to generate and exclude, I don't think this is too far fetched. Symlinks would solve this easily, but they aren't allowed in GitHub Pages. Perhaps there can be rules for GHP using Jekyll with select folders? Dunno the security risks there (perhaps @benbalter can weigh in).

That failing, is it possible to allow for specifying an array of sources?