Keep original file name in main tab when renaming side title bars with /dl /dm /dr

[ldecarufel]

When renaming the side title bars with /dl /dm and /dr, it also renames the filename in the main title tab above the window:

It would be nice to keep displaying the filename in the main tab (or in the main application title), because if there's more than one merge going on, it will be hard to differentiate between them.