How to fix error: You have not concluded your merge (MERGE_HEAD exists) in Git

First, understand what state your repository is in:

# Check the status to see what's happening
git status

You'll see one of these situations:

Situation 1: Unmerged paths (conflicts not resolved)

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:   file.txt

Situation 2: Conflicts resolved but not committed

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

Situation 3: Nothing to commit but merge in progress

On branch main
nothing to commit, working tree clean

(But the error still appears because MERGE_HEAD exists)

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

If there are unresolved conflicts:

# Open conflicted files and resolve them
# Look for conflict markers: <<<<<<<, =======, >>>>>>>

# After resolving, stage the files
git add .

# Complete the merge
git commit -m "Merge branch 'feature' into main"

If conflicts are already resolved:

# Simply commit to finish the merge
git commit -m "Merge branch 'feature' into main"

If there are no changes but Git still complains:

# Create an empty merge commit
git commit --allow-empty -m "Merge commit"

Git will complete the merge and remove the MERGE_HEAD file automatically.

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

git merge --abort

This command:
- Removes the MERGE_HEAD file
- Restores your working directory to the pre-merge state
- Discards any conflict resolutions you made

Important: If you had uncommitted changes before starting the merge, git merge --abort may not be able to restore them. Git will warn you if this is the case.

Alternative using reset:

# This does essentially the same thing
git reset --merge

The --merge flag resets the index and updates files in the working tree that differ between the commit and HEAD, but keeps those that differ between the index and working tree intact.

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

git merge --continue

This is equivalent to running git commit after resolving conflicts. It will:
- Open your editor for a merge commit message (or use the default)
- Create the merge commit
- Clean up MERGE_HEAD

This command was added in Git 2.12 and is the recommended way to complete a merge after conflict resolution.

If other methods don't work (rare), you can manually remove the merge state files:

# Remove merge-related files
rm -f .git/MERGE_HEAD
rm -f .git/MERGE_MSG
rm -f .git/MERGE_MODE

On Windows (Command Prompt):

del .git\MERGE_HEAD
del .git\MERGE_MSG
del .git\MERGE_MODE

On Windows (PowerShell):

Remove-Item .git\MERGE_HEAD -Force
Remove-Item .git\MERGE_MSG -Force -ErrorAction SilentlyContinue
Remove-Item .git\MERGE_MODE -Force -ErrorAction SilentlyContinue

Warning: Only use this as a last resort. This doesn't properly clean up the merge state and may leave your repository in an inconsistent state. After doing this:

# Stage and commit any changes
git add .
git commit -m "Manual cleanup after interrupted merge"

If you had uncommitted changes that complicated the merge, stash them first:

# Stash your current changes
git stash

# Now abort the merge cleanly
git merge --abort

# Pull or merge again
git pull origin main
# or
git merge feature-branch

# Restore your stashed changes
git stash pop

This approach ensures your local work is preserved while you deal with the merge separately.

If stash pop causes conflicts:

# View stashed changes
git stash show -p

# Apply stash without dropping it (safer)
git stash apply

# If successful, drop the stash
git stash drop

After resolving the issue, verify your repository is in a clean state:

# Check status - should show clean working tree
git status

# Verify MERGE_HEAD no longer exists
ls .git/MERGE_HEAD  # Should say "No such file"

# You should now be able to perform Git operations normally
git log --oneline -5  # View recent commits
git branch -a         # List branches

If you completed the merge, you should see your merge commit in the log. If you aborted, you should be back to your previous state.