Understanding and Resolving Git Merge Conflict Diffs

Merge Conflict Diffs

Merge conflicts occur when Git cannot automatically reconcile changes from two branches. Understanding the conflict markers and using diff tools effectively is essential for safe conflict resolution.

Conflict Marker Anatomy

<<<<<<< HEAD
const API_URL = "https://api.staging.example.com";
=======
const API_URL = "https://api.production.example.com";
>>>>>>> feature/deploy-config

• <<<<<<< HEAD — start of your current branch's version
• ======= — separator between the two versions
• >>>>>>> feature/... — end, showing the incoming branch name

Three-Way Diff

A three-way diff shows three versions:

1. Base — the common ancestor (before either branch changed the line)
2. Ours — the current branch (HEAD)
3. Theirs — the incoming branch

BASE:   const API_URL = "https://api.example.com";
OURS:   const API_URL = "https://api.staging.example.com";
THEIRS: const API_URL = "https://api.production.example.com";

Seeing the base version helps you understand the intent of each change.

Conflict Resolution Strategies

Strategy	When to Use
Accept ours	Your branch's change is correct
Accept theirs	Incoming branch's change is correct
Accept both	Both changes are needed (different sections)
Manual merge	Need to combine logic from both versions

Common Conflict Patterns

Both modified the same line:

<<<<<<< HEAD
  timeout: 30,
=======
  timeout: 60,
>>>>>>> feature/performance

Resolution: decide which timeout value is correct, or discuss with the other developer.

Adjacent line modifications:

<<<<<<< HEAD
  host: "localhost",
  port: 3000,
=======
  host: "0.0.0.0",
  port: 8080,
>>>>>>> feature/docker

Resolution: you might need the host from one branch and the port from another.

One branch deleted, another modified:

<<<<<<< HEAD
function legacyHandler() {
  // updated implementation
}
=======
>>>>>>> feature/cleanup

Resolution: decide if the function should be kept (with updates) or deleted.

Best Practices

1. Pull frequently — smaller diffs mean fewer conflicts
2. Use a three-way merge tool — VS Code, IntelliJ, or git mergetool
3. Run tests after resolving — ensure nothing is broken
4. Review the final diff — git diff --staged before committing
5. Communicate — talk to the other developer if unsure about their changes