The problem

You staged the wrong file, wrote a typo in a commit message, and then a commit you pushed broke the VAT totals. Each mistake has its own undo command in git. Some of them only touch your files, some move the branch, and one of them gets back commits that look lost.

You are on main in the invoices repo from the previous chapters, with no uncommitted changes. The last 3 commits on main, newest first, are Add the reduced VAT rate (it adds 2 lines to app/tax.py), Merge branch 'fix-rounding' and Skip empty invoice lines. Each rep starts from this state, plus what its prompt describes.