[sreevisakh]

Other commenters have mentioned interactive and patch staging. That is the standard way to ensure that only the lines you specify go into a commit. I want to add an alternative method that offers some extra advantages.

Patch stack management tools like stacked-git and topgit allow you to setup a number of patches (using git). You can then specify which patch each change goes into. This is sort of like having multiple staging area/indexes at your disposal. They also allow you to add commit messages to each patch at any stage of the development. You could also add, delete, split, squash or edit each patch at any time. And these patches are converted to regular commits at the end of development of the feature. You can also convert any commits into patches if you ever need it.

The attraction that I see in this workflow is that it allows you to combine the chaotic development workflow and final rebasing step into a single stage.