Use init-pants-action in gha workflow (#106)

This shows the new init-pants-action in GHA.

Author: cognifloyd

.github/workflows/pants.yaml

@@ -18,61 +18,38 @@ jobs:
   build:
     name: Perform CI Checks
     needs: org-check
-    env:
-      PANTS_CONFIG_FILES: pants.ci.toml
     runs-on: ubuntu-latest
     strategy:
       matrix:
         python-version: [3.7]
     steps:
     - uses: actions/checkout@v2
-    - name: Get Pants version
-      id: pants_version
-      run: |
-        # Capture the "pants_version = " line from config.
-        PANTS_VERSION=$(grep -E '^pants_version\s*=' pants.toml)
-        echo "::set-output name=pants_version::$PANTS_VERSION"
-    - uses: actions/cache@v2
-      id: cache_pants_setup
-      with:
-        path: |
-          ~/.cache/pants/setup
-        key: pants-setup-${{ steps.pants_version.outputs.pants_version }}
-    - uses: actions/cache@v2
-      id: cached_named_caches
+    - uses: pantsbuild/actions/init-pants@c0ce05ee4ba288bb2a729a2b77294e9cb6ab66f7
+      # This action bootstraps pants and manages 2-3 GHA caches.
+      # See: github.com/pantsbuild/actions/tree/init-pants/
+      # We use an action SHA because there are no tags yet.
       with:
-        path: |
-          ~/.cache/pants/named_caches
+        # cache0 makes it easy to bust the cache if needed
+        # just increase the integer to start with a fresh cache
+        gha-cache-key: cache0-py${{ matrix.python-version }}
         # The Python backend uses named_caches for Pip/PEX state,
-        # so it is appropriate to invalidate on requirements.txt changes.
-        key: pants-named-caches-${{ runner.os }}-${{ hashFiles('pants.toml') }}-${{ hashFiles('requirements.txt') }}
-        # Note that falling back to a restore key may give a useful partial result that will save time
-        # over completely clean state, but will cause the cache entry to grow without bound over time.
+        # so it is appropriate to invalidate on lockfile changes.
+        named-caches-hash: ${{ hashFiles('lockfile.txt') }}
+        # If you're not using a fine-grained remote caching service (see https://www.pantsbuild.org/docs/remote-caching),
+        # then you may also want to preserve the local Pants cache (lmdb_store). However this must invalidate for
+        # changes to any file that can affect the build, so may not be practical in larger repos.
+        # A remote cache service integrates with Pants's fine-grained invalidation and avoids these problems.
+        cache-lmdb-store: 'true'  # defaults to 'false'
+        # Note that named_caches and lmdb_store falls back to partial restore keys which
+        # may give a useful partial result that will save time over completely clean state,
+        # but will cause the cache entry to grow without bound over time.
         # See https://pants.readme.io/docs/using-pants-in-ci for tips on how to periodically clean it up.
-        # Alternatively you may want to avoid using restore keys.
-        restore-keys: |
-          pants-named-caches-${{ runner.os }}-${{ hashFiles('pants.toml') }}-${{ hashFiles('requirements.txt') }}
-          pants-named-caches-${{ runner.os }}-${{ hashFiles('pants.toml') }}-
-          pants-named-caches-${{ runner.os }}-
-    # If you're not using a fine-grained remote caching service (see https://www.pantsbuild.org/docs/remote-caching),
-    # then you may also want to preserve the local Pants cache (lmdb_store). However this must invalidate for
-    # changes to any file that can affect the build, so may not be practical in larger repos.
-    # A remote cache service integrates with Pants's fine-grained invalidation and avoids these problems.
-    - uses: actions/cache@v2
-      id: cache_lmdb_store
-      with:
-        path: |
-          ~/.cache/pants/lmdb_store
-        key: pants-lmdb-store-${{ runner.os }}-${{ hashFiles('**/*') }}
-        # Same caveat as above regarding the issues with restore keys.
-        restore-keys: pants-lmdb-store-${{ runner.os }}-
+        # Alternatively you change gha-cache-key to ignore old caches.
+
     - name: Setup Python ${{ matrix.python-version }}
       uses: actions/setup-python@v1
       with:
         python-version: ${{ matrix.python-version }}
-    - name: Bootstrap Pants
-      run: |
-        ./pants --version
     - name: Check BUILD files
       run: ./pants tailor --check update-build-files --check
     - name: Lint and typecheck