How to undo a git merge with conflicts

When you encounter a conflicting merge in Git, it typically indicates that changes from two branches have been made to the same section of the same file. If you encounter conflicts during a merge and wish to revert the merge, several methods are available to handle this.

Using git merge --abort

If you discover conflicts during the merge and have not yet committed the merge, you can use the following command to abort the merge:

sh
git merge --abort

This reverts to the state before the merge operation, i.e., prior to conflict resolution. Note that this command is only effective if the merge conflicts are encountered before the merge is committed.

Using git reset

If you have already made the merge commit but later decide to revert this merge, you can use the git reset command to reset the HEAD pointer to a specific state. There are two ways to use git reset:

1. Soft Reset: This leaves your working directory unaffected. If you want to keep the changes from the merge but cancel the merge commit, you can use:

   sh
   

git reset --soft HEAD^

shell

   This moves the HEAD pointer back to the commit before the merge commit, but the changes remain in your working directory.

2. Hard Reset: If you want to completely revert the merge including all modifications to the files, you can do the following:

   ```sh
git reset --hard HEAD^

This completely reverts the merge commit and resets your working directory to the state before the merge occurred, discarding all changes made during the merge.

Remember that before performing a hard reset, ensure that you do not need to keep any changes from the merge, as this will clear all uncommitted work.

Using git revert

Sometimes, if the merge has already been pushed to the remote repository, directly resetting may not be advisable as it could affect other collaborators. In this case, you can use git revert to create a new commit that reverts all changes from the previous merge commit.

sh
git revert -m 1 COMMIT_HASH

Here, COMMIT_HASH is the hash of the merge commit. -m 1 specifies the parent number for the main branch, which is typically the first parent of the merge commit.

Using git revert is a safe method to undo changes without rewriting history, especially suitable for branches that have been publicly shared.

Before practicing these commands, it is recommended to perform them on a backup branch to prevent accidental data loss. Additionally, if working in a team environment, it is best to communicate with team members before making such significant changes.