[lmitchell]

So I've actually thought about this a fair bit recently, since I'm making some changes to C++ code that touch a lot of files in reasonably straightforward ways. The changes should be possible to merge conflict-free in basically 100% of cases, but since so many lines are touched, no VCS merge tool can manage it. Most of my changes are just typenames, so I figured, you could do some sort of AST-based merge to allow those changes to merge with semantic changes to the surrounding code.

But this has a lot of problems. Namely - most of the time, when two people change the same line, the changes really do conflict, and someone really does need to manually merge them. In fact, sometimes even when your VCS merges things happily, it still gets them wrong because two changes conflict semantically but don't touch the same lines.

So I guess I would say, I think merging is an impossible problem to 'solve', and going to a more granular merge strategy is actually a move in the wrong direction. You could maybe fix my particular case by 'whitelisting' those typename changes, and saying 'these are allowed to merge with anything else', but at that point... the effort required to specify that unambiguously and make it work properly is probably higher than just merging the changes.