ci: 💚 use sparse checkout and cache properly

Signed-off-by: Eric Nemchik <eric@nemchik.com>

.github/workflows/deploy.yml

@@ -1,38 +1,67 @@
-name: Build mkdocs and deploy to GitHub Pages
+name: Build and Deploy Docs
 
 on: [push, pull_request]
 
 jobs:
+
   build:
     name: Build docs
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4.1.1
-      - uses: actions/setup-python@v5.0.0
+      - name: Checkout repository
+        uses: actions/checkout@v4.1.1
+        with:
+          fetch-depth: 0
+          sparse-checkout: |
+            docs
+      - name: Setup python
+        uses: actions/setup-python@v5.0.0
         with:
           python-version: 3.x
-      - uses: actions/cache@v4.0.0
+      - name: Get pip cache directory
+        id: pip-cache
+        run: |
+          echo "dir=$(pip cache dir)" >> $GITHUB_OUTPUT
+      - name: Cache dependencies
+        uses: actions/cache@v4.0.0
         with:
-          key: ${{ github.ref }}
-          path: .cache
-      - run: pip install -r docs/requirements.txt
-      - run: mkdocs build
+          path: ${{ steps.pip-cache.outputs.dir }}
+          key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
+          restore-keys: |
+            ${{ runner.os }}-pip-
+      - name: Install dependencies
+        run: pip install -r docs/requirements.txt
+      - name: Build documentation
+        run: mkdocs build
 
   deploy:
     if: github.event_name == 'push' && contains(fromJson('["refs/heads/master", "refs/heads/main"]'), github.ref)
     needs: build
     name: Deploy docs
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4.1.1
+      - name: Checkout repository
+        uses: actions/checkout@v4.1.1
         with:
-          fetch-depth: "0"
-      - uses: actions/setup-python@v5.0.0
+          fetch-depth: 0
+          sparse-checkout: |
+            docs
+      - name: Setup python
+        uses: actions/setup-python@v5.0.0
         with:
           python-version: 3.x
-      - uses: actions/cache@v4.0.0
+      - name: Get pip cache directory
+        id: pip-cache
+        run: |
+          echo "dir=$(pip cache dir)" >> $GITHUB_OUTPUT
+      - name: Cache dependencies
+        uses: actions/cache@v4.0.0
         with:
-          key: ${{ github.ref }}
-          path: .cache
-      - run: pip install -r docs/requirements.txt
-      - run: mkdocs gh-deploy --force
+          path: ${{ steps.pip-cache.outputs.dir }}
+          key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
+          restore-keys: |
+            ${{ runner.os }}-pip-
+      - name: Install dependencies
+        run: pip install -r docs/requirements.txt
+      - name: Deploy to GitHub Pages
+        run: mkdocs gh-deploy --force