Add "undo" functionality to edited Flow posts.
This is a prereq for editing other users' posts.
**History page**
For edits to an existing Flow post, the history item should have an (undo) link.
Example:
( cur | prev | topic ) 00:49, 11 February 2015 . . DannyH (WMF) (Talk | contribs | block) edited a comment on "Major misconception of what is a source." . . (-1) (undo) (hide)
**Diff page**
For edits to an existing Flow post, the diff page should have an (undo) link next to the "Version" line.
Example URL: http://flow-tests.wmflabs.org/w/index.php?title=Topic:Sap5csuvzewtf9z4&action=compare-post-revisions&topic_newRevision=sbkkdrvx3hzsd740
Example text:
Version by DannyH (WMF) from 36 minutes ago (undo)
**Undo page**
Clicking an (undo) link takes you to action=edit&undo
Example URL: http://flow-tests.wmflabs.org/w/index.php?title=Chameleons&action=edit&undoafter=557&undo=558
Text:
The edit can be undone. Please check the comparison below to verify that this is what you want to do, and then save the changes below to finish undoing the edit.
Then a comparison of "Latest revision" and "Your text", with an edit window and a save button.
**Error handling**
If the edit can't be undone, go to an undo page with a red error message: "The edit could not be undone due to conflicting intermediate edits."
Example URL: http://flow-tests.wmflabs.org/w/index.php?title=Chameleons&action=edit&undoafter=556&undo=557
**Example screenshots**
Article history page undo link:
{F39169}
Article diff page undo link:
{F39171}
Article action=edit&undo page:
{F39173}
Article undo error handling:
{F39175}
Current Flow history page, no undo link:
{F39177}
Current Flow diff page, no undo link:
{F39179}