Lesson 14 of 20

6 mins read

Merge Conflicts Resolution & git rerere

In Plain English

A merge conflict occurs when two branches modify the exact same lines of code in divergent ways. Git inserts conflict markers (<<<<<<< HEAD, =======, >>>>>>> branch) into the file. Developers resolve the conflict manually, stage the resolved file, and commit. git rerere (Reuse Recorded Resolution) remembers your resolutions automatically.

The Mental Model

"A merge conflict is two co-authors editing paragraph 3 of the same chapter differently: Git highlights both suggestions and asks the lead editor to decide on the final combined sentence."

Deep Dive: How It Works

Conflict Markers: <<<<<<< HEAD (current branch) vs >>>>>>> branch (incoming branch) separated by =======.

Resolution Steps: 1. Edit file to remove markers and keep desired code, 2. git add <file>, 3. git commit.

git rerere: Automatically applies previously recorded conflict resolutions during repeated rebases/merges.

Syntax Blueprint

git config --global rerere.enabled true
git merge feature
# Edit conflict in file.c
git add file.c
git commit -m "merge: resolve feature conflict"

Enable rerere auto-resolution memory, inspect conflict markers, edit, stage, and commit.

Core Rules to Remember

Three-Way Diff: Git compares Base Ancestor, Current HEAD, and Incoming Branch to detect collisions.

Conflict Markers: Always delete all <<<<<<<, =======, and >>>>>>> lines before staging.

rerere Memory: Saves countless hours during long-running rebase trains by remembering how you resolved conflicts.

Common Beginner Traps & How to Fix Them

Mistake:Accidentally leaving <<<<<<< HEAD markers in source files and committing them.

Why it happens: Rushing conflict resolution without testing code compilation.

How to fix: Always build and test project before completing the merge commit.

Pro Tip: Use git checkout --ours <file> or git checkout --theirs <file> to resolve binary or wholesale file conflicts quickly.

Live Interactive Example

Hit Run Code to see it live

Conflict Resolution Simulation

Git 2.45 / CLI

Output Console

Click "Run Code" to view the rendered output.

How it works: Staging the resolved file and committing completes the merge process.

Your Turn: Micro Challenge

No pressure! Edit the starter code below and test your solution with instant feedback.

Micro Exercise

Stage and Commit Conflict Resolution

Write "PORT=8080" to server.env to resolve the conflict.
Stage server.env with "git add server.env".
Commit with message "merge: resolve port conflict".

Sandbox Output

Click "Run & Check" to test your solution.

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