Bitbucket needs a way to download a Pull Request as a patch (text file).

Problem

When a pull request is opened from a fork to the canonical repository, a reviewer of the pull request will be able to see the code in the pull request but may not have permission to view/clone the fork to apply the changes locally.

Suggested solution

• Allow a patch to be downloaded from a pull request.
• Even better would be a tarball of patches created by the equivalent of `git format-patch`.