Patch Operation in Git

Git Patch is a feature in git that allows you to create a patch file (diff file) from changes in one branch and apply those changes to another branch.

• A patch file contains all the differences between branches or commits.
• It helps transfer changes without merging branches directly.
• Useful in code sharing, reviews, or applying selective changes.

Creation and Working of Patches

This process demonstrates how to create a patch from one branch and apply it to another branch.

Step 1: Create Repository & File

Create a new repository named Pat and add a file text.txt inside it.

Step 2: Add & Commit in Master

Stage the file and commit it to the master branch with an initial message.

git add text.txt
git commit -m "initial"

Step 3: Check Logs

View the commit history to verify the changes.

git log

Step 4: Create Feature Branch

Create a new branch named feature and switch to it.

git branch feature
git checkout feature

Step 5: Modify File

Edit the text.txt file by adding some new content.

Step 6: Commit Changes in Feature Branch

Stage and commit the updated file in the feature branch.

git add text.txt
git commit -m "this is in feature branch"

Step 7: Check Logs Again

View the commit history of the feature branch.

git log

Step 8: Create Patch File

Generate a patch file from the feature branch changes.

git format-patch master -o patches

We can also create a patch file using a particular commit's hash key. For example:-

git format-patch -1 012fe999affd9b92f6c96eb72a7260273411ea81 -o patches

The hash key is present in the git log written in dark yellow.  

Step 9: Switch to Master Branch

Move back to the master branch to apply the patch.

git checkout master

Note: Here, "cat text.txt" is used to view the file. This may not run in Windows. Please use Notepad or any code editor to view this.

Step 10: Apply Patch File

Apply the generated patch file to the master branch.

git am patches/<patch-file-name>

Step 11: Verify Changes

Check whether the patch has been successfully applied.

git log
cat text.txt