Setting up ignore file for Mercurial

Im new to Ionic so Im still learning my way around. So far my .hgignore file is set to ignore log and vim’s swp files, but what else can I safely ignore? I thought maybe all the stuff under the build folder should not be in my repo right?

OK, I know its a faux pas but Im an answering my own question here for future reference. I realised today that really the right way to think about this is in the context of a Cordova project and digging around on StackOverflow yielded some answers, the most notable of which being:

and related:

This should be in a FAQ somewhere probably.