I don't mean pull down the whole OS tree from trunk, I mean make your working tree into a git or hg repository.
Text is compressed rather well, so overhead is low even trees with lots of changes and additions. On top of that, its then easy to share the source via github or whatnot, and since to comply with the licenses you have to share the source if you release binaries to the public, that kills two birds with one stone.
The entire linux kernel tree git repository is about 4-500 mb altogether iirc, and that's with the whole 10 years of changes or thereabouts.
Xperia Ray (ST18i) - JB P.A.C.man