Thanks. Could you squash the first commit "Project Organizer: Set header filetype to match source filetype" with the third commit "Combine common code between swap header/source..." so this change is easier to review?
I must say I'm not a big fan of the last commit "Set header filetype to match source filetype". Project organizer, as the name suggests, serves for working with projects and isn't meant to do anything when projects aren't open. There's the "Code navigation plugin" for non-project header/source swapping. So I'd prefer this commit to be removed from this pull request.