Add uv cache busting

CHANGELOG.md

@@ -7,6 +7,17 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ## [Unreleased](https://github.com/hynek/build-and-inspect-python-package/compare/v2.2.1...main)
 
+### Added
+
+- Cache busting for the *uv* cache.
+  GitHub Actions's caching behavior is a bit idiosyncratic:
+  Once a cache is created, it's immutable.
+  But as long as it's accessed within 7 days, it never goes away.
+
+  Therefore, *baipp* now uses the hash of the requirements file as part of the cache key.
+  Behaviorally, nothing changes, except that the cache doesn't grow useless over time.
+  [#115](https://github.com/hynek/build-and-inspect-python-package/pull/115)
+
 
 ## [2.2.1](https://github.com/hynek/build-and-inspect-python-package/compare/v2.2.0...v2.2.1) - 2024-04-02
 

action.yml

@@ -51,15 +51,18 @@ runs:
       run: curl -LsSf https://astral.sh/uv/install.sh | sh
       shell: bash
 
-    - name: Find uv cache
-      run: echo "UV_CACHE=$(uv cache dir)" >>$GITHUB_ENV
+    - name: Find uv cache and hash lock file
+      run: |
+        echo "UV_CACHE=$(uv cache dir)" >>$GITHUB_ENV
+
+        echo "REQS_HASH=$(sha256sum ${{ github.action_path }}/requirements/tools.txt | cut -d' ' -f1)" >>$GITHUB_ENV
       shell: bash
 
     - name: Cache uv
       uses: actions/cache@v4
       with:
         path: ${{ env.UV_CACHE }}
-        key: ${{ runner.os }}-uv
+        key: baipp-${{ env.REQS_HASH }}
 
     - name: Create venv for tools
       run: >