When it comes to the project's .gitignore file, we generally ask developers to follow the recommendations of [Using Git > Ignoring Files](https://help.github.com/articles/ignoring-files), which is to put most ignore rules into either a global .gitignore file or local per-repository .git/info/exclude files. b2g-* is covered by the package rules in the global .gitignore file recommended by that doc, while *.swp seems like the kind of editor-generated file that also makes sense to add to your global .gitignore file.