After the latests composer self-update (Updating to version 321065b), the include-path is getting ignored.
This is used in https://gist.github.com/4124299#file-composer-json, and now I get an error.
Is there a new way of defining include_paths?
The feature definitely didn't get dropped intentionally. It might be a bug resulting from #1420 though (/cc @hason). I will try to look at it later today.
Alright the regression has been fixed by #1424 - can you try to self-update and confirm it works again for you?