want to export tarballs containing only files changed in particular revisions

The "bzr export" command should accept parameters "-r REV1..REV2" and "-c REV" and execute the following process: find all modified files between the two revisions (or the changeset) and generate a tree of these files (in a directory, .zip, etc.). The idea behind this is to be able to send to non-bzr users (and non-VCS users) a "patch" that is applied by copying or unzipping in the right folder (the project folder).

Thus, as an example, if a revision introduces the following changes:
- /a has been added
- /b has been deleted
- /c/d has been modified
- /d/e has been moved to /f
The export command would generate a tree containing:
/a
/c/d
/f
(deleted files are not included)

If these files are zipped into a file - say myPatch.zip - and send to a person, s/he can update her/his working tree by unzipping the file myPatch.zip. This is particularly useful in the context of websites projects: by applying the patch made in the development environment, one is able to update the website which is in the production environment.