[grocery-shopping] Improve verify logic

[jovnc]

Link to exercise: https://git-mastery.org/lessons/commit/exercise-grocery-shopping.html

Description

Verify logic can be improved. Currently, after we first run gitmastery download grocery-shopping then run gitmastery verify without performing any changes, the error message is "all commits are empty", which isn't very useful to users (this should be a check at step 2).

Ideally, we can refactor this such that the verification logic follows the steps for a more logical flow, ie. verify step 1 is complete first before step 2.

Exercise steps

1. Edit it (using any text editor) to remove at least one item from the shopping list and add at least one new item to the shopping list.
2. Stage the change and commit it.

Things to do

• refactor verify logic
• refactor repo-smith tests (if needed)

[desmondwong1215]

May I be assigned to work on this issue? Thank you!