Why conflicts happen

The one case Git can't decide

You changed line 2 of cake.txt on main. Your teammate's branch also changed line 2, differently. Merge them and Git faces two competing truths with no way to know which one you want. It refuses to guess:

$ git merge brown-butter
Auto-merging cake.txt
CONFLICT (content): Merge conflict in cake.txt
Automatic merge failed; fix conflicts and then commit the result.

This is a merge conflict. Two things to internalize before anything else:

• Nothing is broken or lost. Both versions are safely in their commits. Git has simply paused the merge and is waiting for a human decision.
• Conflicts are routine. On a team they happen weekly. Senior engineers read the message and calmly fix it in two minutes, and by the end of this unit you will too.

Reading the conflict markers

Git rewrites the conflicted file to show both versions, fenced by marker lines. Open cake.txt and you'd see:

Preheat oven to 180C
<<<<<<< HEAD
Add regular butter
=======
Add brown butter
>>>>>>> brown-butter
Bake for 25 minutes

Decoding it:

• <<<<<<< HEAD starts your side: what the line looks like where you stand (HEAD, your current branch, here main).
• ======= is the divider between the two versions.
• >>>>>>> brown-butter ends their side: the incoming branch's version.
• Everything outside the markers (Preheat..., Bake...) merged fine and needs no attention.

The conflict is only the marked region. A 500-line file with one conflicted line needs one decision, not 500.