Understanding Git: Differences Between `merge --squash` and `rebase`

When collaborating on code, it’s crucial to maintain a clean and understandable project history. Git provides a plethora of tools to manage the changes made to a repository, two of which are `merge --squash` and `rebase`. While they might seem similar at first glance, they serve different purposes and produce different outcomes. Below, we dive into the technical distinctions between `merge --squash` and `rebase`, complemented with examples for clarity.

Git Basics

Before exploring the differences, it's essential to understand some basic concepts:

• Branching: In Git, a branch represents an independent line of development. Branches allow you to develop features, fix bugs, or experiment in isolation.
• Commits: Each commit in Git records a snapshot of all the files in your project at a given point in time.
• Merging: Merging is the process of integrating changes from one branch into another.

`merge --squash`

The `merge --squash` command in Git is used to combine changes from one branch with another, resulting in a single new commit on the target branch. It does not create a merge commit, and the source branch's history is not retained in the target branch.

Characteristics:

• Squashed Commits: All commits from the source branch are combined into a single commit in the target branch.
• No Merge Commit: Unlike a normal merge, it doesn’t create a merge commit.
• History Alteration: The historical commits from the source branch are not visible after the merge.

Example:

Imagine you have a feature branch called `feature-login` with three commits. To integrate this branch into the `main` branch using `merge --squash`, you’d perform the following steps:

• Linear History: Incorporates all commits from the source branch in sequence after the current branch’s commits.
• Interactive Options: Allows editing, reordering, or squashing of commits during the rebase process.
• History Rewriting: Modifies the commit history by creating new commits.
  • Use `merge --squash` when you want a simple history in the target branch and the branch’s internal history isn’t crucial.
  • Use `rebase` for cleaner, linear history, especially useful when preparing a feature branch for integration after updates to the main branch.
  • When working in a team, it's critical to communicate about when and how to use these commands to prevent potential data loss and ensure a clear history.
  • While `merge --squash` doesn’t alter the originally shared history, `rebase` can rewrite commit history. Ensure shared changes aren’t rewritten without consensus.