Fixed issue #2676: Swapped Theirs and Mine in Edit conflicts outside of rebase dialog on rebasing

Merged username-removed-112407 requested to merge issue-2676 into master

This is not limited to vanilla git rebase: Even if we use our own rebase dialog and open edit conflicts outside the dialog, we get swapped diffs.

This MR tries to fix both use cases.

@ch3cooli Comments?