Saw code in one of my files at a WIP merge request.
Wanted to add something to fix a bug.
Added, tested and committed.
Pushed.
Wondered why my change wasn't listed in the "changes" section of the merge request.

Turned out that I accidentally edited a file that had the same piece of code where I wanted to add something.
Well, lucky me! If I wouldn't have been editing the "wrong" file accidentally, i probably would have spent hours of debugging only to find out that I am actually in the real wrong file.