How to fix fatal: You have not concluded your merge (MERGE_HEAD exists). Please, commit your changes before you merge. in Git

First, understand the current state of your repository:

git status

This will show you one of several possible states:

If all conflicts are resolved:

On branch main
All conflicts fixed but you are still merging.
  (use "git commit" to conclude merge)

If conflicts still exist:

On branch main
You have unmerged paths.
  (fix conflicts and run "git commit")
  (use "git merge --abort" to abort the merge)

Unmerged paths:
  both modified:   filename.txt

This status tells you exactly what needs to be done next.

If you want to keep the merge changes, complete it by committing:

If all conflicts are already resolved:

git commit -m "Merge branch 'feature-branch' into main"

Git may open your default editor for a merge commit message. Save and close to complete.

If conflicts still need resolution:

1. Open each conflicting file and resolve the conflicts (look for <<<<<<<, =======, and >>>>>>> markers)

2. After resolving each file, stage it:

git add <resolved-file>

3. Once all conflicts are resolved, commit:

git commit -m "Merge branch 'feature-branch' into main"

Using git merge --continue:

If you've already resolved all conflicts and staged the files, you can also use:

git merge --continue

This is equivalent to running git commit and will finalize the merge.

If you want to cancel the merge and return to the state before it started:

git merge --abort

This command will:
- Remove the MERGE_HEAD file
- Reset your working directory to the state before the merge
- Discard any conflict resolutions you made

If git merge --abort fails:

Sometimes you may see: "Entry 'filename' not uptodate. Cannot merge."

In this case, first stage your changes:

git add .
git merge --abort

Alternative - git reset:

For older Git versions (before 1.7.4), use:

git reset --merge

This achieves the same result as git merge --abort.

If the above methods don't work, you can perform a hard reset:

Warning: This will discard ALL uncommitted changes in your working directory.

git reset --hard HEAD

This resets your branch to the last commit, removing the merge state and any uncommitted changes.

If you need to reset to a specific commit:

# View recent commits
git log --oneline -5

# Reset to a specific commit
git reset --hard <commit-hash>

Last resort - manually remove MERGE_HEAD:

If Git commands are still not working, you can manually delete the merge state files:

rm -f .git/MERGE_HEAD
rm -f .git/MERGE_MSG
rm -f .git/MERGE_MODE

After this, run git status to verify the merge state is cleared. Note that this may leave your working directory in an inconsistent state, so review your files carefully.

After completing or aborting the merge, verify everything is working:

# Check status - should show clean working tree
git status

# Verify MERGE_HEAD is gone
ls .git/MERGE_HEAD 2>/dev/null || echo "MERGE_HEAD cleared"

# Test that other operations work
git log --oneline -3

You should now be able to:
- Checkout other branches
- Pull from remote
- Start new merges
- Perform other Git operations normally