How to Squash Multiple Commits in Git: A Comprehensive Guide

Introduction

In version control with Git, maintaining a clean commit history is often desirable for readability and tracking changes efficiently. Sometimes you may want to combine multiple commits into one, either for clarity or simplicity before sharing your work with others. This process is known as "squashing" commits. In this tutorial, we will explore how to squash the last N commits in Git using different methods.

Understanding Commit Squashing

Squashing is useful when you have several small commits that relate to a single change or feature. Instead of having numerous commits cluttering your history, squashing allows you to condense these into a single commit. This can make it easier for others (and yourself) to understand the project history.

Methods to Squash Commits

We’ll cover three main methods: using git reset, git rebase, and git merge --squash.

Method 1: Using Git Reset

This method is straightforward and doesn’t require altering commit order.

1. Soft Reset:

   • Use the command git reset --soft HEAD~N where N is the number of commits you want to squash.
   • This resets your branch to N commits ago but keeps the changes in your working directory ready for a new commit.

2. Create New Commit:

   git commit -m "New combined commit message"
   

3. Force Push (if needed):
   If you’ve already pushed these commits, use git push --force-with-lease <branch-name> to update the remote branch safely.

Method 2: Using Git Rebase

This interactive method is more flexible and allows you to edit commit messages as well.

1. Start Interactive Rebase:

   git rebase -i HEAD~N
   

   This command opens an editor with the last N commits listed from oldest to newest.

2. Edit Commit List:

   • Change pick to squash (or s) for all but the first commit you want to squash into.
   • Alternatively, use fixup (or f) if you don’t need to keep the commit messages from those commits.

3. Update Commit Messages:
   If squashing or using squash, you’ll be prompted to edit the commit message for the new combined commit.

4. Complete Rebase:
   Save and close the editor to complete the rebase process.

5. Force Push (if needed):
   Similar to the reset method, use git push --force-with-lease <branch-name> if you need to update a remote branch.

Method 3: Using Git Merge –Squash

This technique is useful for creating a single commit that represents the changes from multiple commits without altering history before it’s squashed.

1. Reset Head:

   git reset --hard HEAD~N
   

2. Merge with Squash:

   git merge --squash HEAD@{1}
   

   This command stages all changes from the last N commits as a single commit without making any new commits.

3. Commit Changes:
   The editor will open allowing you to use existing commit messages or create a new one.

   git commit -m "New combined commit message"
   

4. Force Push (if needed):
   Use git push --force-with-lease <branch-name> as necessary.

Best Practices

• Always ensure your working directory is clean before starting these operations to avoid losing work.
• Communicate with your team if you’re squashing commits on a shared branch, especially when force-pushing changes.
• Consider using git reflog to recover from mistakes or unintended state after a reset or rebase.

Conclusion

Squashing commits in Git can greatly improve the clarity of your project’s history. Whether through a simple reset for immediate cases, an interactive rebase for more control and message editing, or a merge squash for pre-push consolidation, you now have several tools at your disposal to maintain clean commit histories efficiently.