Edit history for Issue and PR comments

[fnordsh]

Feature Description

It would be very helpful if issue and pr comments had an edit history, like github has.

Every comment that has been edited should have a message informing the user about when and by whom the comment was last edited. Ideally, it should also have a way to view older versions and/or diffs.

Currently, there is no such indication, so people could, for example, make a popular comment and after getting approval from others change the content of the original comment to create a false impression for anyone coming late to the discussion.

This is made worse by the fact that by default, every user with write permissions can change every other user's comments without any indication that this has happened - see #17585.

Screenshots

[wxiaoguang]

We already have it (in 1.16, I submitted the PR)

• Save and view issue/comment content history #16909

Try it on try.gitea.io