If you do a merge incorrectly, then discard it, then do the “same” merge again, it will be incorrect again. You can forget a recorded resolution, though. From the documentation:
git rerere forget <pathspec>This resets the conflict resolutions which rerere has recorded for the current conflict in
<pathspec>.
Be careful to use it on specific paths; you don’t want to blow away all of your recorded resolutions everywhere. (forget with no arguments has been deprecated to save you from doing this, unless you type git rerere forget . to explicitly request it.)
But if you don’t think to do that, you could easily end up putting that incorrect merge into your history..