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

git-cola is a great GUI and also has this feature built-in. Just select the lines to stage and press S. If no selection is made, the complete hunk is staged.