Summary: Merge conflicts

The one-sentence definition

A merge conflict is git asking you a question: “two branches changed these same lines in different ways; please tell me which version you want.”

The six-step resolution

1. Recognize: git status shows “Unmerged paths”
2. Find: open each conflicting file; locate <<<<<<< markers
3. Decide: choose your version, their version, both combined, or new
4. Edit: write the resolution; delete all marker lines
5. Stage: git add <file>
6. Commit: git commit

Enable diff3 (one-time setup)

git config --global merge.conflictstyle diff3
# or the modern alternative:
git config --global merge.conflictstyle zdiff3

Shows the common ancestor in conflict markers. Strictly better than the default.

The five conflict types

Type	What it looks like	Fix
Textual	<<<<<<< markers in the file	Read both sides; pick one or combine; remove markers
Logical combine	Markers around adjacent changes	Combine both changes; write a test for the combined behavior
Semantic	NO markers; auto-merge succeeded	Integration tests catch it; review with the merged result in mind
Delete-modify	”deleted by us / modified by them”	git rm (delete wins) or git add (modify wins)
Rename-edit	Two paths with overlapping content	Apply edits to the new path; git rm the old path

When to abort

git merge --abort

When: conflicts too large to resolve calmly, wrong branch checked out, teammate’s branch has unexpected commits, you’re tired. Abort is not failure; it’s taking a do-over.

Conflict prevention (in order of leverage)

1. Rebase often: small daily conflicts beat one massive one later
2. Small PRs: short-lived branches diverge less
3. Communicate big refactors: five minutes prevents days
4. Avoid long-lived branches: feature flags + small PRs beat 3-week branches
5. Clear ownership boundaries: two engineers on different modules conflict less

Stay-calm psychology

• Nothing is destroyed. Both branches’ work is safe.
• The merge can be undone with git merge --abort.
• The mechanics are mechanical. Six steps.

What you carry into L8

You can resolve any conflict you’ll hit in two-person collaboration. L8 covers the final Phase 2 topic: how branches travel across repositories (remotes, forks, push, fetch, pull).

Voice anchor

Git stores snapshots. Every other command is just navigating those snapshots.

A conflict is git asking which snapshot to make current. The resolution is your answer.