Manual shellcheck (#321)

.github/workflows/knative-style.yaml

@@ -1,15 +1,31 @@
 # Copyright 2020 The Knative Authors.
 # SPDX-License-Identifier: Apache-2.0
 
-# This file is automagically synced here from github.com/knative-extensions/knobots
+# This file is manually placed. Not using github.com/knative-extensions/knobots
+# The reasons are outlined in https://github.com/knative/infra/issues/207
+# Explaination of options https://github.com/reviewdog/action-shellcheck
 
-name: Code Style
+name: shellcheck_reviewdog
 
 on:
   pull_request:
     branches: [ 'main', 'release-*' ]
 
 jobs:
-
-  style:
-    uses: knative/actions/.github/workflows/reusable-style.yaml@main
+  shellcheck:
+    name: "manual / shellcheck"
+    description: "Uses reviewdog to suggest shell script format changes. Enforces ShellCheck."
+    runs-on: ubuntu-latest
+        steps:
+          - uses: actions/checkout@v4
+          - name: "ShellCheck"
+            uses: reviewdog/action-shellcheck@v1
+            with:
+              reporter: 'github-pr-review'
+              pattern: "*.sh"
+              filter_mode: 'diff_context'
+              exclude: |
+                ./vendor/*
+                */vendor/*
+              shellcheck_flags: |
+                --external-sources -e=SC1091