Scenario 01: Track a config file and make it machine-specific

User Prompt

I want to track my ~/.gitconfig with chezmoi. My work laptop uses alice@corp.com as the git email but my personal machine uses alice@personal.com. Make it work on both.

Expected Behavior

1. Run chezmoi add ~/.gitconfig to start tracking the file
2. Convert to a template with chezmoi chattr +template ~/.gitconfig (or chezmoi add --template ~/.gitconfig)
3. Edit the source file (chezmoi edit ~/.gitconfig) and replace the hardcoded email with {{ .chezmoi.hostname }} or a custom data variable
4. Show the user how to add machine-specific data in chezmoi.toml under [data]
5. Verify with chezmoi cat ~/.gitconfig before applying
6. Apply with chezmoi apply

Success Criteria

• Tracks file with chezmoi add
• Converts to template — source file has .tmpl suffix
• Uses a template variable (.chezmoi.hostname, .chezmoi.os, or custom data) to differentiate machines
• Shows chezmoi cat or chezmoi execute-template to preview before applying
• Does NOT hardcode the email difference as two separate files

Failure Conditions

• Suggests managing two separate dotfile repos for each machine
• Hardcodes hostname comparison without explaining how to set custom data
• Skips the preview step and goes straight to apply
• Forgets to show how to commit and push the change to git