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-meld-index -- quoting from the website:

git-meld-index runs meld -- or any other git difftool (kdiff3, diffuse, etc.) -- to allow you to interactively stage changes to the git index (also known as the git staging area).

This is similar to the functionality of git add -p, and git add --interactive. In some cases meld is easier / quicker to use than git add -p. That's because meld allows you, for example, to:

• see more context
• see intra-line diffs
• edit by hand and see 'live' diff updates (updated after every keypress)
• navigate to a change without saying 'n' to every change you want to skip

Usage

In a git repository, run:

git meld-index

You'll see meld (or your configured git difftool) pop up with:

LEFT: temporary directory contining files copied from your working tree

RIGHT: temporary directory with the contents of the index. This also includes files that are not yet in the index but are modified or untracked in the working copy -- in this case you'll see the file contents from HEAD.

Edit the index (right hand side) until happy. Remember to save when needed.

When you're done, close meld, and git-meld-index will update the index to match the contents of the temporary directory on the right hand side of meld that you just edited.