segmentio/metalsmith-collections — pull request #19 by anthonyshort (2014-08-12 20:56:35+00:00)
Title: Added the ability to add content to multiple collections

This lets you do

```
---
title: My Awesome Page
collection:
- Favourites
- Travel
- Shopping
---
```

or

```
---
title: My Awesome Page
collection: Favourites
---
```

This only thing I'm not sure of is what line 41 was being used for, since that will reset the collections array on the file.