How to stage selected parts of the changes?

git add -p

To stage only selected parts of your changes use git add -p.

Git will show parts of your changes one by one and let you decide what to do with that change.

The available actions for the given hunk are:
 y - stage this hunk
 n - do not stage this hunk
 q - quit staging hunks
 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
 K - leave this hunk undecided, see previous hunk
 g - select a hunk to go to
 / - search for a hunk matching the given regex
 s - split the current hunk into smaller hunks
 e - manually edit the current hunk
 ? - print help

After selecting an action for the given hunk, git will show the next available hunk. In the example below, both hunks are staged with typing y.

git add -p

diff --git a/articles_controller.rb b/articles_controller.rb

index cd678a9..ea67e94 100644

--- a/articles_controller.rb

+++ b/articles_controller.rb

@@ -1,4 +1,8 @@

 class ArticlesController < ApplicationController

+  def index

+    @articles = Article.all

+  end

+

   def show

     @article = Article.find(params[:id])

   end

(1/2) Stage this hunk [y,n,q,a,d,j,J,g,/,e,?]? y

@@ -7,4 +11,13 @@ class ArticlesController < ApplicationController

     @article = Article.new

   end

+  def create

+    @article = Article.new(title: "...", body: "...")

+

+    if @article.save

+      redirect_to @article

+    else

+      render :new

+    end

+  end

 end

(2/2) Stage this hunk [y,n,q,a,d,K,g,/,e,?]? y

See git add to learn more about it.