Add shell script pre-commit hooks

Now that software updates are handled by a bash script that is stored
in the repository these pre-commit hooks should be re-added to the
pre-commit configuration. This also includes re-adding all of the
scaffolding that installs the shfmt tool in the build.yml workflow.

.github/workflows/build.yml

@@ -15,23 +15,46 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
+      - id: setup-env
+        uses: cisagov/setup-env-github-action@develop
       - uses: actions/checkout@v2
       - id: setup-python
         uses: actions/setup-python@v2
         with:
           python-version: "3.10"
+      # We need the Go version and Go cache location for the actions/cache step,
+      # so the Go installation must happen before that.
+      - uses: actions/setup-go@v2
+        with:
+          go-version: '1.16'
+      - name: Store installed Go version
+        id: go-version
+        run: |
+          echo "::set-output name=version::"\
+          "$(go version | sed 's/^go version go\([0-9.]\+\) .*/\1/')"
+      - name: Lookup Go cache directory
+        id: go-cache
+        run: |
+          echo "::set-output name=dir::$(go env GOCACHE)"
       - uses: actions/cache@v2
         env:
           BASE_CACHE_KEY: "${{ github.job }}-${{ runner.os }}-\
-            py${{ steps.setup-python.outputs.python-version }}"
+            py${{ steps.setup-python.outputs.python-version }}-\
+            go${{ steps.go-version.outputs.version }}-"
         with:
           path: |
             ${{ env.PIP_CACHE_DIR }}
             ${{ env.PRE_COMMIT_CACHE_DIR }}
+            ${{ steps.go-cache.outputs.dir }}
           key: "${{ env.BASE_CACHE_KEY }}\
             ${{ hashFiles('**/.pre-commit-config.yaml') }}"
           restore-keys: |
             ${{ env.BASE_CACHE_KEY }}
+      - name: Install shfmt
+        env:
+          PACKAGE_URL: mvdan.cc/sh/v3/cmd/shfmt
+          PACKAGE_VERSION: ${{ steps.setup-env.outputs.shfmt-version }}
+        run: go install ${PACKAGE_URL}@${PACKAGE_VERSION}
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip setuptools wheel

.pre-commit-config.yaml

@@ -46,3 +46,23 @@ repos:
       - id: yamllint
         args:
           - --strict
+
+  # Shell script hooks
+  - repo: https://github.com/cisagov/pre-commit-shfmt
+    rev: v0.0.2
+    hooks:
+      - id: shfmt
+        args:
+          # Indent by two spaces
+          - -i
+          - '2'
+          # Binary operators may start a line
+          - -bn
+          # Switch cases are indented
+          - -ci
+          # Redirect operators are followed by a space
+          - -sr
+  - repo: https://github.com/detailyang/pre-commit-shell
+    rev: 1.0.5
+    hooks:
+      - id: shell-lint