Compare 2 versions of a file

[AndyScherzinger]

Provide an option to compare 2 versions of a file by marking them and opening both side-by-side in some kind of a "dual-pane", so the user can scroll both to visually compare them.

[artonge]

What file formats should be covered by that feature?
Should the files be editable on that view? Might be problematic for files like spreadsheets.

One option could be to generate a picture of both files, compare those pictures to create a diff, and overlay the diff on both files. Might not be easy, but would be generic.

The non-generic way would be to implement a diff algo for each file format. Maybe there is some open source one available already.

[AndyScherzinger]

The idea is to just display 2 versions next to each other for the ones where we have a viewer available.
Like with viewing the version see #39139 any version should be read-only except for the current version

[jancborchardt]

@nextcloud/designers it would be good to have a mockup for this, how to select the 2 versions and compare them. :)