Change 350191 had a related patch set uploaded (by WMDE-Fisch):
[mediawiki/extensions/TwoColConflict@master] [WIP] Add selection dialog for the base version

https://gerrit.wikimedia.org/r/350191

@Lea_WMDE @Jan_Dittrich When the user selects "My text" and the editor then contains his text the description above the editor needs to change.

So what should the user see there?

( currently: )

Initially, the editor's content is the currently published version:
127.0.0.1‎
Add your changes in the editor and click on "publish changes"

So what should the user see there?

@Lea_WMDE @WMDE-Fisch
As far as I know:

If javascript is enabled, and chosing a version thus possible, the text above the editor is at start (as in the mock above)

»
1) Choose the base version in the popup below.
2) Adjust the text to combine both versions.
3) Click on „Publish changes“. Only what is in the editor will be published.
«

Once the user did the selection (that was what you were asking for, if I got it right), the text could stay as it is – it is still valid.
But if we find it confusing, we could gray out and/or checkmark line 1 (or something in that direction)

Ahh... ok it was not really clear to me that in the JS version with base version selection the text stays the same after the selection. Thanks!

Graying out the first step after the selection might be a nice thing though. But this can also be decided later and done in a small follow up.

Patch is now ready to be reviewed. Hint for the reviewers:

Ignore the layout of the left column. On master this does not match the mock (yet) and does not need to. It is unrelated to this ticket.

Change 350191 merged by jenkins-bot:
[mediawiki/extensions/TwoColConflict@master] Add selection dialog for the base version

https://gerrit.wikimedia.org/r/350191

One thing that I noticed here when reviewing the next patch in the chain was that the selection dialogue is positioned right at the top of the input box.

This differs from the mock and I image we will want to add some space there @WMDE-Fisch, @Jan_Dittrich

Yes, we should have some margin because it otherwise looks like it somehow is attached to the toolbar.