Interactive Rebasing for History

Welcome to a powerful Git tool: interactive rebase! It allows you to rewrite your project's commit history before sharing it with others.

Think of it as a time machine for your commits, letting you clean up, combine, or reorder changes to create a clear, linear story of your work.

Why would you want to rewrite history?

• Clarity: Make your project's commit log easy to read and understand.
• Conciseness: Combine small, incremental commits into a single, meaningful change.
• Debugging: A clean history helps when using tools like git bisect to find where a bug was introduced.
• Better Pull Requests: Present a polished set of changes to collaborators.

To start an interactive rebase, you'll use the git rebase -i command. You need to specify how far back you want to go.

For example, to rebase the last 3 commits on your current branch, you'd use:

This opens an editor showing your last 3 commits and available commands.

When you start an interactive rebase, Git opens a text editor with a list of commits and instructions. Each commit starts with a command:

• pick: Use the commit as is.
• reword: Use the commit, but edit its message.
• edit: Use the commit, but pause to amend changes.
• squash: Combine with the previous commit, merging messages.
• fixup: Combine with the previous commit, discarding this commit's message.
• drop: Remove the commit entirely.

Let's say you made a typo in a commit message. You can use reword to fix it. Change pick to reword next to the commit you want to change:

pick 5a6b7c8 Add new feature
pick 1d2e3f4 Fix typo in docs
reword 9g0h1i2 Implement login screen

After saving and closing the editor, Git will prompt you to edit the message for the 9g0h1i2 commit.

Often, you make several small, related commits that could be one. Use squash to combine them.

pick a1b2c3d Initial feature commit
squash e4f5g6h Add more details
fixup i7j8k9l Fix small bug

Here, e4f5g6h will merge into a1b2c3d, combining their messages. i7j8k9l will also merge into a1b2c3d, but its message will be discarded (fixup).

If you have an experimental commit you no longer need, you can simply drop it from history. Just change pick to drop or delete the line entirely:

pick 1122334 Initial setup
drop 5566778 Test experimental feature
pick 9900112 Add user authentication

After saving, the commit 5566778 will be completely removed from your branch's history.

You can also change the order of commits. Simply cut and paste lines in the editor to rearrange them. Git will apply the changes in the new order.

Original order:

pick abcdef1 Add feature A
pick 1234567 Add feature B

Reordered:

pick 1234567 Add feature B
pick abcdef1 Add feature A

Be cautious, as reordering might introduce conflicts if commits depend on each other.

This is crucial: Never rebase commits that have already been pushed to a shared remote repository (like GitHub or GitLab) and might have been pulled by others.

Rebasing rewrites commit IDs. If others have based their work on the original commits, your rebased commits will appear as a completely different history, causing major conflicts and confusion for everyone involved.

Only rebase commits that exist solely on your local branch!

You have three commits: A (Initial), B (Minor fix), C (Refactor). You want to combine B into A, keeping A's original message, and then keep C as is. Which commands would you use in the interactive rebase editor (from oldest to newest)?

You've learned about the powerful git rebase -i command!

• It allows you to rewrite your local commit history.
• You can reword messages, squash or fixup commits, drop unwanted changes, and even reorder commits.
• Always remember the golden rule: NEVER rebase commits that have already been pushed to a shared remote.

Mastering interactive rebase helps maintain a clean, understandable project history!