Idea: Diff output mode

[mlatysh]

Hi Repomix Team!

I’d like to propose an enhancement that could be very useful for code reviews and tracking changes.

Currently, Repomix outputs the whole repository as one file, which is great—but it would be even more powerful if there were an option to generate a hybrid output. In this mode, the full project is included as usual, but files that are “affixed” or flagged for change would be presented in a diff format (for example, showing the differences between branches or between the current state and a specific branch). Meanwhile, all other files would be displayed in their standard format.

This hybrid mode would allow AI reviewers to easily see what has changed without duplicating the entire codebase for both states. It would combine a complete view of the repository with a clear, focused diff for files that have been modified, streamlining the review process and helping to quickly identify important changes.

Thanks!