Beacuse Eric Sink is a smart guy, but he doesn't understand git yet. He's still following the Subversion workflow. The secret is that "git commit" is not a sacred act. Don't be fooled by the words. When you do an "svn commit", the result is written in stone in some centralized repository where it can break everyone else's builds, now and forever. When you do a "git commit" the result sits on your machine. It goes nowhere. This is distributed version control -- a commit just changes your local repo, and if it doesn't work you just undo it. (Or, alternatively, make seven more commits in your efforts to fix it, then use the mighty "git rebase --interactive" to smash all of them together into a single, perfect commit. Then you pretend that it was correct all along. Nobody else will be the wiser. You'll look like a genius!)

So, if you want to pull half the hunks out of a previous commit, make a branch (you can make branches more easily than blinking -- this is git), pull out half the hunks, commit the result. Then compile and test. (If you like, you can probably use a post-commit hook to compile and test automatically.) If the tests pass, merge your experimental branch back into your development branch, then do the "git push" to the central repository. It is that push -- not any of your commits -- that is the point where you have to be sure that you're not breaking anything. And you can't use git's index to push files that have never been visible to your compiler and your tests.

UPDATE: I have yet to actually use them, but another one of Sink's commenters reminds me that git has pre-commit hooks that seem to solve his specific problem. Here's something I googled up on that subject:

http://www.nabble.com/git-pre-commit-hook--best-place-to-mak...

Again, I don't use such a thing, because I think it's kind of silly to insist that every local commit pass all tests. That's a recipe for failing to make enough local commits. I've been finding that it's better to make a commit every time you make any change that can be described in an English sentence. Then you have a little log of everything that you've done that you can rearrange with "git rebase -i" and turn into your final, pushable commits.

Most of the startups we funded in our Boston cycles didn't come from Boston, and practically all left Boston afterward. We could have been anywhere. Anywhere with decent coffee at least.

Honestly, they'd have done better to just fund 20 startups in Boulder rather than 10 in one place and 10 in another.

A philosophy is warm fuzzies, but the contract that is the TOS is what matters.

Unlike, say, photography. Or cooking. Or music. Or...

He kinda lost me there. You are not a beautiful and unique snowflake.