Golden rule of rebasing (never rebase public) in Git - Time & Space Complexity

Time Complexity: Golden rule of rebasing (never rebase public)

O(n)

Understanding Time Complexity

When using git rebase, it's important to understand how the operation scales with the number of commits involved.

We want to see how the work git does grows as more commits are rebased.

Scenario Under Consideration

Analyze the time complexity of rebasing a branch with multiple commits.

git checkout feature-branch
# feature-branch has 50 commits

git rebase main
# main has new commits since feature-branch started

This rebases the feature branch commits onto the updated main branch.

Identify Repeating Operations

Look for repeated steps git performs during rebase.

• Primary operation: Applying each commit one by one onto the new base.
• How many times: Once for each commit in the feature branch (e.g., 50 times).

How Execution Grows With Input

As the number of commits to rebase increases, git must apply each commit in order.

Input Size (n)	Approx. Operations
10 commits	10 apply steps
100 commits	100 apply steps
1000 commits	1000 apply steps

Pattern observation: The work grows directly with the number of commits to rebase.

Final Time Complexity

Time Complexity: O(n)

This means the time to rebase grows linearly with the number of commits being rebased.

Common Mistake

[X] Wrong: "Rebasing a public branch is safe and has no impact on others."

[OK] Correct: Rebasing rewrites commit history, so if others use that branch, their work will conflict and cause confusion.

Interview Connect

Understanding how git rebase scales and why rebasing public branches is risky shows you grasp both git mechanics and teamwork impact.

Self-Check

"What if we rebase a branch with only one commit? How does the time complexity change?"

Practice

1. What is the main reason for the golden rule of rebasing: never rebase public?

easy

A. Rebasing public branches speeds up the repository cloning process.

B. Rebasing public branches can rewrite shared history and confuse collaborators.

C. Rebasing public branches automatically merges all conflicts.

D. Rebasing public branches deletes all previous commits permanently.

Solution

1. Step 1: Understand what rebasing does

   Rebasing rewrites commit history by moving commits to a new base.

2. Step 2: Consider the effect on public branches

   If you rebase a branch others use, their history conflicts with the rewritten one, causing confusion and errors.

3. Final Answer:

   Rebasing public branches can rewrite shared history and confuse collaborators. -> Option B

4. Quick Check:

   Rebasing public = rewrite shared history = confusion [OK]

Hint: Never rebase branches others already use to avoid conflicts [OK]

Common Mistakes:

• Thinking rebasing speeds cloning
• Believing rebasing auto-resolves conflicts
• Assuming rebasing deletes commits permanently

2. Which of the following is the correct git command to rebase your current branch onto main?

easy

A. git rebase main

B. git rebase -m main

C. git rebase --merge main

D. git rebase --onto main

Solution

1. Step 1: Recall basic rebase syntax

   The command to rebase the current branch onto another is git rebase <branch>.

2. Step 2: Check options given

   Only git rebase main matches the correct syntax to rebase onto main.

3. Final Answer:

   git rebase main -> Option A

4. Quick Check:

   Basic rebase syntax = git rebase branch [OK]

Hint: Use 'git rebase branchname' to rebase current branch [OK]

Common Mistakes:

• Adding unnecessary flags like -m or --merge
• Using --onto incorrectly without extra arguments
• Confusing rebase with merge commands

3. You have a local branch feature that you rebased onto main. What happens if you try to push it to a remote where feature was already shared without force?

medium

A. Push merges remote changes automatically.

B. Push succeeds and overwrites remote history automatically.

C. Push deletes the remote branch.

D. Push is rejected because history has diverged.

Solution

1. Step 1: Understand rebasing effect on commit history

   Rebasing rewrites commits, so local branch history differs from remote.

2. Step 2: Consider git push behavior

   Git refuses to push if histories diverge to prevent overwriting others' work unless forced.

3. Final Answer:

   Push is rejected because history has diverged. -> Option D

4. Quick Check:

   Rebase + push without force = rejected [OK]

Hint: Push after rebase needs --force or fails [OK]

Common Mistakes:

• Assuming push overwrites remote without force
• Thinking push merges automatically
• Believing push deletes remote branch

4. You accidentally rebased a public branch and now collaborators have conflicts. What is the best way to fix this?

medium

A. Delete the remote branch and recreate it from scratch.

B. Tell collaborators to reset their branches to the new history.

C. Force push the rebased branch and ask collaborators to rebase or reset.

D. Merge the rebased branch into main to fix conflicts.

Solution

1. Step 1: Understand the problem caused by rebasing public branch

   Rebasing rewrites history, so collaborators' copies conflict with the new history.

2. Step 2: Fix by force pushing and coordinating with collaborators

   Force push updates remote with new history; collaborators must rebase or reset to sync.

3. Final Answer:

   Force push the rebased branch and ask collaborators to rebase or reset. -> Option C

4. Quick Check:

   Fix rebase public = force push + collaborator reset [OK]

Hint: Force push and coordinate resets after rebasing public branch [OK]

Common Mistakes:

• Expecting collaborators to fix without reset
• Deleting remote branch unnecessarily
• Merging rebased branch to fix history

5. You want to keep your commit history clean by rebasing, but your branch feature is already pushed and shared. What is the safest workflow to update your branch without breaking the golden rule?

hard

A. Create a new local branch from main, cherry-pick your commits, then push as a new branch.

B. Rebase the shared feature branch directly and force push.

C. Merge main into feature instead of rebasing.

D. Delete the remote feature branch and push your rebased branch with the same name.

Solution

1. Step 1: Avoid rebasing a shared branch directly

   Rebasing shared branches breaks history for others, so avoid it.

2. Step 2: Use a new local branch and cherry-pick commits

   Create a fresh branch from main, apply your commits cleanly, then push as new branch to avoid rewriting shared history.

3. Final Answer:

   Create a new local branch from main, cherry-pick your commits, then push as a new branch. -> Option A

4. Quick Check:

   Keep history clean = new branch + cherry-pick + push new [OK]

Hint: Use new branch + cherry-pick to avoid rebasing shared branches [OK]

Common Mistakes:

• Force pushing rebased shared branch
• Merging instead of rebasing when clean history needed
• Deleting remote branch unnecessarily