Git: Should I ignore the Index or is there a killer application for it?

Question

As a subversion user, git's index is the most challenging new concept I'm facing as I consider using it for new projects. I read many people's comments saying that they don't use the Index (always commit -a) but I'm thinking there might be a killer reason out there as to why I would want to make use of it. (I'm sharing code with around 5 other developers, working in a mature development environment where we merge code to test and stable branches and use branching for experimental or significant new features.)

Answer 1

You know that the index lets you only commit parts of the files that you want to add to the repository, of course. In general, I find it useful for this reason. I can make changes to files that sort of work, check in the parts that work, and then complete and check in the rest.

For a really killer demonstration; try using interactive add, or patch add (using git add -i, or git add -p). This runs through all your changes and lets you selectively add them to the index. This lets you make a whole load of changes to your files and yet split the commits. Useful for those 'aha' fixes that we all make from time to time.

Have a look at this screencast to see how it's done. Not till you try it yourself will you see how useful it is.