smerge-refine
smerge-refine is an interactive compiled Lisp function in `smerge-mode.el
'.
(smerge-refine &optional PART)
Highlight the words of the conflict that are different.
For 3-way conflicts, highlights only two of the three parts.
A numeric argument PART can be used to specify which two parts;
repeating the command will highlight other two parts.