There is a lot of peer review happening before a patch is proposed for inclusion in the mainline. (Look for "commit fest" to learn about the details.)
Of course, you could separate those into chunks that can each be attributed to exactly one person. But why should you? I'd rather have one good patch by author A, based on an idea by B, prototype by C, reviewed by D, with additional documentation editing by E instead of a dozen crappy commits mixed with another dozen small cleanups "to serve the pure git workflow".