Fix #38321 -- Provide navigation through git merge conflicts with codelens

[andrewtomai]

#38321
It should first be noted that the "next conflict" and "previous conflict" buttons will not be present if there is only 1 merge conflict in the current file.

It should also be noted that this navigation does not go between files. For example, if there are 2 conflicts in file A and 2 conflicts in file B, the "next conflict" button will not ever switch between the two files.

[msftclas]

All CLA requirements met.

[chrmarti]

Thanks @andrewtomai !

I don't like that this makes the list of code lenses even longer:

[chrmarti]

I suggest to add 'Previous Merge Conflict' and 'Next Merge Conflict' toolbar items to the editor when there are merge conflicts instead of the proposed change here. That will also cover part of the pain point discussed in #47886.

[chrmarti]

Here is an example of how to conditionally show actions in the editor context menu, a similar approach can be used here:

• The 'when' condition using 'openCloudConsoleCount': https://github.com/Microsoft/vscode-azure-account/blob/19d85880f993ecc626e20da4f7da184528ff3e88/package.json#L86
• Setting the 'openCloudConsoleCount' context: https://github.com/Microsoft/vscode-azure-account/blob/19d85880f993ecc626e20da4f7da184528ff3e88/src/cloudConsole.ts#L186

The diff editor already comes with previous/next toolbar items, yours could look the same:

[andrewtomai]

Okay! Ill attempt to make this change!

[isuvorov]

+1

[Yukioru]

+1

[FDiskas]

Why the merge tool is so ugly? Looks like somebody got brainfart implementing this :D
Ok sorry, but could you do this in better way?
Like it is done "Sublime merge", "JetBrains"

It's almost done by clicking on "Compare Changes" but it's read only. So lets do it this way - make left side (local copy) editable so the user just could copy some stuff from incoming changes.

As a solution currently I'm using online tool to compare and apply changes :D