tailwind2-1  Exercise 1: What Gets Scanned
=======================================

Run this in an empty folder that has Tailwind installed (npm install tailwindcss @tailwindcss/cli). It is bash; on Windows use Git Bash.

rm -rf audit && mkdir -p audit/src audit/node_modules/ui-kit audit/dist audit/content audit/assets && cd audit
git init -q
printf 'dist/\n' > .gitignore
echo '<p class="text-red-500">page</p>'               > src/index.html
echo 'Use <span class="text-green-500">green</span>'   > content/post.md
echo 'export const c = "text-blue-500";'               > node_modules/ui-kit/widget.js
echo '<p class="text-yellow-500">built</p>'            > dist/built.html
echo '.text-purple-500 { color: purple; }'             > src/old.css
printf 'text-pink-500'                                 > assets/logo.png
echo '@import "tailwindcss";' > input.css
check() { npx @tailwindcss/cli -i "$1" -o out.css >/dev/null 2>&1
  for c in red green blue yellow purple pink; do grep -q "^  \.text-$c-500 " out.css && printf '%s ' $c; done; echo; }
echo "1) defaults:";                  check input.css
cat > step2.css <<'EOF'
@import "tailwindcss";
@source "./node_modules/ui-kit";
EOF
echo "2) + @source ./node_modules/ui-kit:";        check step2.css
cat > step3.css <<'EOF'
@import "tailwindcss";
@source "./node_modules/ui-kit";
@source not "./content";
EOF
echo "3) + @source not ./content:";   check step3.css
cat > step4.css <<'EOF'
@import "tailwindcss" source(none);
@source "./src";
@source "./node_modules/ui-kit";
EOF
echo "4) source(none) + two folders:" ; check step4.css

Output:

1) defaults:
red green 
2) + @source ./node_modules/ui-kit:
red green blue 
3) + @source not ./content:
red blue 
4) source(none) + two folders:
red blue

WHY THIS WORKS AS AN ANSWER
---------------------------
Prediction for step 1 (defaults): red (src/index.html), green (the Markdown post: any text file is scanned). Not blue (node_modules is always skipped), not yellow (dist/ is in .gitignore),
not purple (CSS files are never scanned), not pink (a PNG is binary). The run agrees. There is no git repo problem either: the script runs git init, but the ignore file is read without one too.
Step 2: @source "./node_modules/ui-kit" adds that folder and overrides the node_modules rule, so blue appears. Step 3: @source not "./content" drops the Markdown post, so green goes.
Step 4: source(none) turns the automatic scan off, so only the folders you list are read: src and node_modules/ui-kit. The result is the same red and blue, but now it is the whole list of
what Tailwind may read, instead of a list of exceptions. purple and pink never appear in any step, because a file type that is not scanned stays unscanned even if you name its folder.