Add caching for uv and .venv directories in CI

Author: gvanrossum-ms

.github/workflows/ci.yml

@@ -1,3 +1,4 @@
+# .github/workflows/ci.yml
 name: CI
 on: [push, pull_request]
 
@@ -14,9 +15,20 @@ jobs:
           - { name: "make format --check", cmd: "make format FLAGS=--check" }
     steps:
       - uses: actions/checkout@v4
+
+      - name: Cache uv
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cache/uv
+            .venv
+          key: ${{ runner.os }}-uv-${{ hashFiles('**/uv.lock', '**/pyproject.toml') }}
+          restore-keys: ${{ runner.os }}-uv-
+
       - name: Install uv
         run: |
           set -euxo pipefail
           curl -LsSf https://astral.sh/uv/install.sh | sh
           echo "$HOME/.local/bin" >> $GITHUB_PATH
+
       - run: ${{ matrix.cmd }}