How to undo a Git merge that hasn’t been pushed yet?

To undo a Git merge that hasn’t been pushed yet, use git reset to revert your branch to the state before the merge. Here’s how to do it safely:

Step-by-Step Solution

1. Check the current state (optional):

   git status  # Ensure you're in a clean state

2. Reset to the pre-merge commit:

• Use ORIG_HEAD (Git’s reference to the commit before the merge):
  bash
  • git reset --hard ORIG_HEAD
• OR use the specific commit hash (found via git reflog):
  bash
  • git reset --hard <commit-hash-before-merge>

Key Notes

• Works for un-pushed merges: This method is safe if you haven’t pushed the merge to a remote repository.
• Loses uncommitted changes: Use git stash first if you have unsaved work.
• For conflicted merges: If the merge was interrupted (e.g., due to conflicts), use:

  git merge --abort  # Aborts the merge process entirely

Example Workflow

# Start a merge (e.g., git merge feature-branch)
# Realize the merge is incorrect

# Undo the merge:
git reset --hard ORIG_HEAD

# Verify the log:
git log --oneline  # The merge commit is gone

What If the Merge Was Fast-Forwarded?

If the merge was a fast-forward (no merge commit created), use:

git reset --hard HEAD@{1}  # Revert to the previous state

Clean Up Untracked Files (Optional)

After undoing the merge, remove any leftover files:

git clean -fd  # Deletes untracked files/directories (use with caution!)

Summary

Scenario	Command
Undo a completed merge	git reset --hard ORIG_HEAD
Abort a conflicted merge	git merge --abort
Undo fast-forward merge	git reset --hard HEAD@{1}

Once reset, you can re-attempt the merge or push your branch safely.