Comment 8 for bug 672530

The story is "As a user, I want to see a diff that ignores changes in whitespace, so I can see the important change to the text."

At the moment they can say "--diff-options -w" but as Paul points out this is a bit longwinded.

We can implement '-w' as an option to bzr diff. To start with, it can shell out to gnu diff, and fail (perhaps cleanly) if you don't have an external diff. Later on we can do it in process, which will be better for people on non-gnu systems.