How to easily undo a git rebase

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Undoing a Git rebase can be essential if the rebase didn’t go as planned or introduced unexpected conflicts or issues. The easiest way to undo a rebase is by using the git reflog command to find the commit hash of the state before the rebase and then resetting your branch to that commit using git reset --hard. This method ensures that you can safely revert to the previous state before the rebase was initiated.

Using Git Reflog

Step-by-Step Process:
To undo a rebase using git reflog:

  1. View Reflog:

    git reflog
    • Displays a list of actions (including rebases) and their corresponding commit hashes.

  2. Identify Commit:

    • Locate the commit hash before the rebase started. This is typically labeled with "rebase" in the reflog output.

  3. Reset to Commit:

    git reset --hard
    • “: The hash of the commit before the rebase.

Example:

git reflog
# Output example
# abcdef1 (HEAD -> master) HEAD@{0}: rebase: checkout abcdef1
# ghijk12 HEAD@{1}: commit: Your last commit message before rebase
# lmnop34 HEAD@{2}: checkout: moving from feature to master

# Identify commit before rebase, e.g., ghijk12
git reset --hard ghijk12
  • This example reverts the branch to its state before the rebase began.

Using ORIG_HEAD

Automatic Reference:
Git automatically saves the previous position of HEAD before dangerous operations like rebase:

  1. Reset Using ORIG_HEAD: 
    git reset --hard ORIG_HEAD
    • ORIG_HEAD: Points to the commit before the last rebase.

Example:

git rebase branchA
# Rebase completes but you want to undo it
git reset --hard ORIG_HEAD
  • Quickly reverts to the state before the rebase operation.

Aborting an Ongoing Rebase

If Conflicts Occur:
If you’re in the middle of a rebase and encounter conflicts:

  1. Abort Rebase: 
    git rebase --abort
    • Aborts the rebase and returns to the original branch state.

Example:

git rebase branchB
# Conflicts occur
git rebase --abort
  • Aborts the rebase process and resets to the pre-rebase state.

Using Backup Branch

Proactive Measure:
Create a backup branch before rebasing:

  1. Create Backup:

    git checkout -b backup-branch
    • Creates a branch at the current state.

  2. Rebase:

    git rebase branchC

  3. Restore from Backup:

    git checkout original-branch
git reset --hard backup-branch
    • Restores the original branch from the backup.

Example:

git checkout -b backup-before-rebase
git rebase branchD
# If issues occur
git checkout original-branch
git reset --hard backup-before-rebase
  • Ensures a safe point to return to if rebase issues arise.

Reverting Specific Commits

Selective Undo:
To undo specific commits introduced by rebase:

  1. Identify Commits:

    git log
    • Find commit hashes to revert.

  2. Revert Commits:

    git revert
    • Reverts specific commits without undoing the entire rebase.

Example:

git log
# Identify commits to revert, e.g., commit_hash1
git revert commit_hash1
  • Reverts specific rebase commits selectively.

Summary

Undoing a Git rebase is straightforward using git reflog to identify the previous commit state and git reset --hard to revert to it. The ORIG_HEAD reference provides a quick undo option immediately after a rebase. For ongoing rebase conflicts, git rebase --abort is effective. Creating a backup branch before rebasing ensures an additional layer of safety, and selectively reverting specific commits offers fine-grained control over the rebase changes. These methods provide flexibility and reliability in managing rebase operations and ensuring a stable codebase.

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