Is there a way to tell Perforce to leave text files alone without setting the file-type as binary? Or barring that, is there a way to tell the Perforce client to diff binaries?
Set all of your client/workspace specs to 'unix' line-endings. Then no conversion will take place when you check in on Windows.
See http://answers.perforce.com/articles/KB_Article/CR-LF-Issues-and-Text-Line-endings/