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Exercises — Stage 4: Try a Branch ​

Exercise 1: Switch back and forth ​

Goal: Feel what "switching branches" actually does.

Steps:

  1. Run git checkout main. Check git branch — asterisk is on main.
  2. Reload index.html in your browser. Exactly the same.
  3. Run git checkout dark-theme. Check git branch — asterisk is on dark-theme.
  4. Reload again. Still exactly the same.

What happened: Because both branches point at the same commit, switching between them changes nothing on disk. Branches diverge only after you commit something new on one of them.

Exercise 2: Peek at the branch label files ​

Goal: Prove that a branch is literally just a file pointing at a commit hash.

Steps:

  1. Run cat .git/refs/heads/main.
  2. Run cat .git/refs/heads/dark-theme.

What happened: Both commands print the same 40-character commit hash. That is the entire mechanism of branching — two small files holding the same hash. When you commit on dark-theme, only that file updates.

Exercise 3: Create and delete a throwaway branch ​

Goal: Learn how to clean up experimental branches.

Steps:

  1. Run git checkout -b scratch.
  2. Run git branch — you now have three branches.
  3. Run git checkout dark-theme.
  4. Run git branch -d scratch.
  5. Run git branch — scratch is gone.

What happened: git branch -d <name> deletes a branch label. It is safe here because scratch had no unique commits. Git refuses to delete a branch with commits that are not merged anywhere — it uses capital -D for that.

Exercise 4: See where HEAD points ​

Goal: Understand the HEAD concept.

Steps:

  1. Run cat .git/HEAD.

What happened: You see something like ref: refs/heads/dark-theme. HEAD is Git's note-to-self about which branch you currently have checked out. When you switch branches, Git updates this one file.