Commit only part of a file in Git

Question

When I make changes to a file in Git, how can I commit only some of the changes?

For example, how could I commit only 15 lines out of 30 lines that have been changed

Answer 1

For Atom users, the package github includes interactive staging, in the style of git gui. For shortcuts see the package's documentation.

Using Atom allows working with a theme that has dark background (by default, git gui has a white background).