Staging patches with Git add -p

# Staging patches with git add Source: [https://www.simonholywell.com/post/git-add-p/](https://www.simonholywell.com/post/git-add-p/) ## Introduction If you’re not already using`git add \-p`to stage your commits then you’re missing out\. It allows you to interactively stage a file or just part of it giving you greater control over your git commit process\. ## Why should you want to do this? Here are some of the reasons why I prefer using`git add \-p`in my workflow\. Primarily, because it allows me to review my changes as I stage them and I often find mistakes this way\. By reviewing changes during staging, I catch bugs, typos, and other issues that might have slipped through during initial coding or content creation\. There is an additional benefit though; it allows me to stage only part of file\. Git, rather oddly, refers to these parts as hunks so I will use that term going forward\. This feature is really useful when you have a number changes, but you want to group them up into different commits\. Imagine you’ve made several related changes across different parts of a file\. With`git add \-p`, you can selectively stage these changes together, ensuring cleaner and more organized commits\. ## Staging part of a file Here is an example of the interface showing you the diff and then prompting you to “Stage this hunk?”\. ``` diff --git a/main.mts b/main.mts index e1132f2..8f7c279 100644 --- a/main.mts +++ b/main.mts @@ -1,2 +1,4 @@ export const add = (a, b) => a + b +export const div = (a, b) => a / b export const sum = (xs) => xs.reduce((acc, x) => sum(acc, x)) +export const avg = (xs) => div(sum(xs), xs.length) (1/1) Stage this hunk [y,n,q,a,d,s,e,?]? ``` In its simplest form we can enter`y`to stage that diff ready for commit or`n`not to\. For this example I am not ready to commit the`avg`function, but I want to get`div`pushed up so I choose to enter`s`to split the hunk into smaller hunks\. Git then asks me this\. ``` Split into 2 hunks. @@ -1,2 +1,3 @@ export const add = (a, b) => a + b +export const div = (a, b) => a / b export const sum = (xs) => xs.reduce((acc, x) => sum(acc, x)) (1/2) Stage this hunk [y,n,q,a,d,j,J,g,/,e,?]? ``` So I enter`y`to stage that hunk for commit and git responds with the next hunk\. ``` @@ -2 +3,2 @@ export const sum = (xs) => xs.reduce((acc, x) => sum(acc, x)) +export const avg = (xs) => div(sum(xs), xs.length) (2/2) Stage this hunk [y,n,q,a,d,K,g,/,e,?]? ``` Remembering that I only want to commit the`div`function I then enter`q`to quit the interactive hunk staging\. After interacting with the hunk staging, I return to the command prompt\. From there, I can proceed with git commit or any other necessary commands\. ## Checking it worked If I were to run a`git status`to check the staged files I would see that the fil \(`main\.mts`\) appears in both sections; to be committed and not staged for commit\. This is because we only staged part of the file and it is what we wanted\! ``` On branch main Your branch is ahead of 'origin/main' by 1 commit. (use "git push" to publish your local commits) Changes to be committed: (use "git restore --staged <file>..." to unstage) modified: main.mts Changes not staged for commit: (use "git add/rm <file>..." to update what will be committed) (use "git restore <file>..." to discard changes in working directory) modified: main.mts ``` By selectively staging only part of the file, we’ve successfully prepared a single hunk—a patch—for our upcoming commit\. ## Other options The list \(`\[y,n,q,a,d,s,e,?\]`\) of potential responses is shortened, but you can get extended information by entering`?`to get the help documentation\. Here are some response options you can use during interactive hunk staging taken from the[git documentation](https://git-scm.com/book/en/v2/Git-Tools-Interactive-Staging#_staging_patches)\. You’ll notice that there are a lot more options than in the list we saw earlier\. - `y`: stage this hunk - `n`: do not stage this hunk - `a`: stage this and all the remaining hunks in the file - `d`: do not stage this hunk nor any of the remaining 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 - `k`: leave this hunk undecided, see previous undecided hunk - `K`: leave this hunk undecided, see previous hunk - `s`: split the current hunk into smaller hunks - `e`: manually edit the current hunk - `?`: print help ## When not to use it I use`git add \-p`nearly every time I commit every working day\. There are two occasions where I don’t: 1. There is a newly created file to commit for the first time \- when a file is newly created there is no previous version to diff against of course so`git add \-p`cannot present a diff for you to approve for staging\. 2. In rare cases, when I want to commit an entire directory and am confident about its content, I usually opt for the standard approach\. However, even in such edge cases, I often find myself using git add \-p for finer control\. ## Conclusion By incorporating`git add \-p`into your workflow, you’ll streamline your git and commit process\.\. I use this technique, without exaggeration, nearly every single time I need to commit a changeset to git\. It allows me to easily review my code as I stage it for commit and control exactly what goes into each of my commits\.