From the post:
Git is an excellent tool for collaborative software development in a number of ways. In my opinion, Git’s most valuable feature – which also happens to be one of its most underappreciated – is interactive staging: git add -i and git add -p. If you are a software development who does not use Git, or if you use Git but do not use this feature, you should not write another line of code until you learn it.
Source: The number one reason to start using git: interactive staging