Jake Worth

Commit Part of a File in Git

Published: May 06, 2022 2 min read

  • git

You’ve been working on a big set of changes, and haven’t committed to Git yet. Now, you want to commit some, but not all, changes to a file.

Or maybe you want to make a series of small commits that break your work down into understandable chunks. Great idea!

Or, maybe you know some of your unstaged changes are bad, and you want to leave them off the final product.

The tool you need is:

$ git add --patch

--patch lets you interactively choose which changes to apply to a commit.

Applying Patches

Run this command and you’ll see the following:

$ git add --patch
diff --git a/README.md b/README.md
index 18d277a..b012031 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,7 @@
 # [jakeworth][production-url]

+A blog of awesome Git tricks.
+
(1/2) Stage this hunk [y,n,q,a,d,j,J,g,/,e,?]? ?

This is a piece of our diff, or a ‘hunk’, with information telling us which one we are currently reviewing (one of two), and a menu of options.

Type ?, to learn about each option.

y - stage this hunk
n - do not stage this hunk
q - quit; do not stage this hunk or any of the remaining ones
a - stage this hunk and all later hunks in the file
d - do not stage this hunk or any of the later hunks in the file
g - select a hunk to go to
/ - search for a hunk matching the given regex
j - leave this hunk undecided, see next undecided hunk
J - leave this hunk undecided, see next hunk
e - manually edit the current hunk
? - print help

What you do next is up to you. I approach this with the following thought process:

  1. Am I seeing too many changes at once? Or, would I like to keep some but not all of them? Split the hunks with s to consider each separately.
  2. For each hunk, do I want to commit it now? y or n.
  3. Or, do I know I want to add all the changes to the file? a.
  4. Or, discard the changes to the file? d.
  5. Do I want to edit this change? e, although this can be tricky if you aren’t comfortable editing diffs.

Consider each hunk, then commit the hunks you said y, or a, e to with:

$ git commit

Going Further

This is the only way that I commit, even for small changes. Why? I find it’s a nice default. And even for those small changes, I often am surprised to realize that I can break them down even more when reviewing them one-by-one.

To help, I’ve aliased this to gap, a trick I picked up at Hashrocket.

alias gap='git add --patch'

This flag also applies to git checkout, which is handy. Use it to checkout changes to a file, in pieces:

$ git checkout --patch

Do you --patch? Got another approach? Let me know in the comments.

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Blog of Jake Worth, software engineer in Maine.

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