Dev a working on the header and dev b working on the footer is an ideal case that actually never occurred to me. Most of the time they work on both. And any good versioning tool properly used should help avoid conflict, no matter if the coffee is in the same file or not.

It's not like we are doing c or java under cvs, we don't have to split in minuscule files, therefore maybe we shouldn't, in python, js, or css dialects.