World 3: Parallel Universes

A branch is a sticky note

You will learn: what a branch really is, and how to make one.

The problem

You want to try a dark theme for your diary. But main must keep working. Where can you play safely?

Watch

A is a sticky note on a commit. git branch dark-mode sticks a new note here. You stay where you are.

Try it

Make a branch called dark-mode.

Hint

Type git branch dark-mode, then press Enter.

Watch

~/diary $ git branch dark-mode~/diary $ git branch  dark-mode* main

git branch with no name lists your notes. The star marks the one you are on.

Try it

Notes can go on old commits too. Stick a note called idea on “Add day 1 page”.

Tap a commit. Then stick a new branch on it.

Predict

You are on main. You make a new commit. Which note moves forward?

Check

See? Only main moved. HEAD rides along on main. dark-mode waits on the old commit.

You did it!

You can now make branches and see what they really are.

Go deeper (optional)

git branch -v shows the commit under each note. git branch -m dark-mode night-mode renames one. Branch names can’t have spaces. Teams use - and /, like feature/dark-mode. Why are branches so cheap? Inside Git, a branch is just a name holding one commit id.

~/diary $ git branch dark-mode~/diary $ git branch -v  dark-mode 270a76e Add style* main      270a76e Add style