Git Squash vs Merge: What’s the Difference and When to Use Each?

Git Squash vs Merge: What’s the Difference and When to Use Each? | Image Credit: Git Squash Docs

Git Squash vs Merge: What’s the Difference and When to Use Each?

In the realm of Git, merging changes from one branch to another is a fundamental operation. However, developers often encounter the choice between using a standard git merge and a git merge --squash, or even considering interactive rebase for squashing. Understanding the nuances of each approach, including their impact on the commit history and workflow, is crucial for effective version control. This article provides a detailed comparison of Git squash and merge, outlining their differences and guiding developers on when to strategically employ each method.

Understanding Git Merge

The standard git merge command integrates changes from a specified branch into your current branch. It preserves the entire commit history of the source branch, creating a new \"merge commit\" that links the histories of the two branches.

git checkout main;\ngit merge feature_branch;

A merge commit typically has two parent commits: the tip of the current branch and the tip of the branch being merged.

Understanding Git Squash

Git squash, achieved primarily through git merge --squash or interactive rebase (git rebase -i), consolidates the commits from a branch into a single new commit on the target branch. This results in a linear and cleaner commit history, hiding the intermediate steps taken during feature development.

git checkout main;\ngit merge --squash feature_branch;\ngit commit -m \"Merged feature X with squashed commits\";

When using --squash, no merge commit is created. Instead, the changes are staged, and you create a new commit summarizing all the changes from the merged branch.

Key Differences: Squash vs. Merge

The core difference lies in how the commit history is represented:

• Commit History:
  • Merge: Preserves the full commit history of the merged branch, including individual development steps, and creates a merge commit.
  • Squash: Creates a single new commit representing all the changes from the merged branch, resulting in a linear history without the individual steps or a merge commit (when using merge --squash). Interactive rebase offers more granular control over which commits are squashed and their order.
• Complexity of History:
  • Merge: Leads to a more complex history with branching and merging points, which can be beneficial for tracking the evolution of features.
  • Squash: Results in a simpler, linear history, making it easier to follow the major changes introduced.
• Impact on Remote Branches:
  • Merge: Merging a branch and pushing the result is a straightforward operation.
  • Squash (via Rebase): Squashing commits that have already been pushed to a shared remote branch requires a force push (git push --force), which can be disruptive and should be done with extreme caution. git merge --squash avoids rewriting history on the feature branch itself.

When to Use Git Merge

• Preserving Detailed History: When it's important to retain the complete history of a feature branch, including all the incremental commits.
• Long-Lived Feature Branches: For long-lived feature branches where the individual commits might hold significance over time.
• Collaboration on Feature Branches: When multiple developers are working on the same feature branch and the individual commits represent their specific contributions.
• Clear Branching Structure: When you want to explicitly show the branching and merging points in the project's history.

When to Use Git Squash (via git merge --squash or git rebase -i)

• Cleaning Up Feature Branches Before Merging: To present a cleaner, more concise history of a feature when merging it into the main branch.
• Simplifying the Main Branch History: To keep the main branch history linear and focused on significant feature integrations.
• Reducing Noise in Commit Logs: When a feature involved many small, self-contained commits.
• Collaborative Agreement: When the team has a convention of squashing feature branches before merging.
• Initial Development Cleanup: Squashing all initial commits on a local branch before the first push.

Interactive Rebase (git rebase -i) for Squashing

Interactive rebase offers the most flexibility for squashing. It allows you to pick, squash, fixup, reorder, and drop commits, and edit commit messages.

Conclusion

The choice between Git squash and merge depends on the specific needs of your project and your team's workflow preferences. git merge preserves detailed history, while git squash creates a cleaner, more linear history. Understanding the trade-offs will empower you to make informed decisions.