The diff API is kind of incomplete. Scenario:
- have 2 temporary files, none of them come from the IDE
- create editable diff controller for them
- edit the right file
- close the diff's "JComponent" by pressing OK button
- now what??
There is no documented way how to:
- find out whether the "right" file has been changed? and/or
- save the modified document?, and/or
- get the content of the modified "right" file.
Thanks a lot.
BTW this  is what I need to do in order to use the Diff API for my (not so uncommon, I would say) needs. Please notice that the save() method must be always called (even if user clicks Cancel) otherwise the IDE thinks that there is a file with unsaved changes somewhere.
Integrated into 'main-golden', will be available in build *201203210400* on http://bits.netbeans.org/dev/nightly/ (upload may still be in progress)
User: Tomas Mysik <firstname.lastname@example.org>
Log: Editable diff works now
But really too much complicated, issue #208740 should solve this.