For a book you may use one file per chapter, for an article a unique file - always in a formatting word processor. Sure, it would be nice to have a version control system working transparently withing the word processor, namely recognizing changes paragraph by paragraph.
I know of two professional writers who use Emacs.
Neal Stephenson: If you are a professional writer--i.e., if someone else is getting paid to worry about how your words are formatted and printed--emacs outshines all other editing software in approximately the same way that the noonday sun does the stars.
http://artlung.com/smorgasborg/C_R_Y_P_T_O_N_O_M_I_C_O_N.sht...
Vernor Vinge also uses Emacs, and RCS for version control:
http://www.norwescon.org/archives/norwescon33/vingeinterview...
I'm under the impression that many fiction writers work with straight, unformatted text.
I don't know anyone who would ever write a manuscript as
collection of text files. This is non sense.
I would think it wouldn't be too hard to write a little program that lets you edit visually, then stores the proper text file on disc and commits it whenever you save. Or maybe commits when you tell it to, giving you a chance to enter a commit message that means something.
I don't know anyone who would ever write a manuscript as collection of text
files.