title = Update files in the index
cards = add commit

[description]

When we change files, the index won't change on its own. We have to use `git add` to update the index to the changed version of the file.

Let's try that!

[setup]

echo "The candle is burning with a blue flame." > candle
git add .
git commit -m "The beginning"

[win]

# Make a change to the candle.
test "$(git diff --name-only)" = "candle" || file -f .git/candle-changed && touch .git/candle-changed

# Add the candle.
test "$(git diff --cached --name-only)" = "candle" || file -f .git/candle-added && touch .git/candle-added

# Make a commit.
test "$(git diff --name-only HEAD HEAD^)" = "candle"