Editor: nano

By default nano quietly adds linebreaks to the file that you're working on, not just word-wraps it for display in the editor. This can cause trouble with generating patches, and because it's indistinguishable from word-wrapping in the editor, it can take you a while to diagnose it. To prevent this from happening, when you call nano, do it with the -w flag, which will turn off auto-linebreaking:

You may want to make this a default by aliasing the command:

Now, whenever you run 'nano', it'll run 'nano -w' instead.