GHA: Add Lint workflow that uses pants

.github/workflows/lint.yaml

@@ -0,0 +1,88 @@
+---
+# This Lint workflow uses pants
+name: Lint
+
+on:
+  push:
+    branches:
+      # only on merges to master branch
+      - master
+      # and version branches, which only include minor versions (eg: v3.4)
+      - v[0-9]+.[0-9]+
+    tags:
+      # also version tags, which include bugfix releases (eg: v3.4.0)
+      - v[0-9]+.[0-9]+.[0-9]+
+  pull_request:
+    type: [opened, reopened, edited]
+    branches:
+      # Only for PRs targeting those branches
+      - master
+      - v[0-9]+.[0-9]+
+  schedule:
+    # run every night at midnight
+    - cron:  '0 0 * * *'
+
+jobs:
+  # Lint checks which don't depend on any service containes, etc. to be running.
+  lint-checks:
+    name: 'Lint Checks (pants runs: shellcheck)'
+    runs-on: ubuntu-latest
+
+    env:
+      COLUMNS: '120'
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+        with:
+          # a test uses a submodule, and pants needs access to it to calculate deps.
+          submodules: 'true'
+
+      #- name: Cache APT Dependencies
+      #  id: cache-apt-deps
+      #  uses: actions/cache@v2
+      #  with:
+      #    path: |
+      #      ~/apt_cache
+      #    key: ${{ runner.os }}-apt-v7-${{ hashFiles('scripts/github/apt-packages.txt') }}
+      #    restore-keys: |
+      #      ${{ runner.os }}-apt-v7-
+      - name: Install APT Depedencies
+        env:
+          CACHE_HIT: 'false' # cache doesn't work
+          #CACHE_HIT: ${{steps.cache-apt-deps.outputs.cache-hit}}
+        run: |
+          # install dev dependencies for Python YAML and LDAP packages
+          # https://github.com/StackStorm/st2-auth-ldap
+          ./scripts/github/install-apt-packages-use-cache.sh
+
+      - name: Initialize Pants and its GHA caches
+        uses: pantsbuild/actions/init-pants@c0ce05ee4ba288bb2a729a2b77294e9cb6ab66f7
+        # This action adds an env var to make pants use both pants.ci.toml & pants.toml.
+        # This action also creates 3 GHA caches (1 is optional).
+        # - `pants-setup` has the bootsrapped pants install
+        # - `pants-named-caches` has pip/wheel and PEX caches
+        # - `pants-lmdb-store` has the fine-grained process cache.
+        #   If we ever use a remote cache, then we can drop this.
+        #   Otherwise, we may need an additional workflow or job to delete old caches
+        #   if they are not expiring fast enough, and we hit the GHA 10GB per repo max.
+        with:
+          base-branch: master
+          # To ignore a bad cache, bump the cache* integer.
+          gha-cache-key: cache0
+          # This hash should include all of our lockfiles so that the pip/pex caches
+          # get invalidated on any transitive dependency update.
+          named-caches-hash: ${{ hashFiles('requirements.txt') }}
+          # enable the optional lmdb_store cache since we're not using remote caching.
+          cache-lmdb-store: 'true'
+
+      - name: Lint
+        run: |
+          ./pants lint ::
+
+      - name: Upload pants log
+        uses: actions/upload-artifact@v2
+        with:
+          name: pants-log-py${{ matrix.python-version }}
+          path: .pants.d/pants.log
+        if: always()  # We want the log even on failures.