Run shellcheck on github actions

Author: fredemmott

.github/shellcheck.sh

@@ -0,0 +1,30 @@
+#!/bin/bash
+shellcheck "$0"
+FAILURES=()
+for FILE in bin/*; do
+  read -r FIRST_LINE < "$FILE"
+  if [ "${FIRST_LINE}" = "#!/bin/sh" ] || [ "${FIRST_LINE}" = "#!/bin/bash" ]; then
+    echo "::group::${FILE}"
+    if ! shellcheck --color=always "$FILE"; then
+      FAILURES+=("$FILE")
+      # Re-run, but take JSON and convert it to the format documented here:
+      # https://docs.github.com/en/actions/learn-github-actions/workflow-commands-for-github-actions#setting-an-error-message
+      shellcheck -f json "$FILE" | jq -r '.[] | "::error file=\(.file),line=\(.line),col=\(.column),endColumn=\(.endColumn),title=SC\(.code): \(.message)::For more information, see https://www.shellcheck.org/wiki/SC\(.code)"'
+    else
+      echo "No errors."
+    fi
+    echo "::endgroup::"
+  else
+    echo "::debug::Skipping $FILE, not a shell script."
+  fi
+done
+
+if [ "${#FAILURES[@]}" -ne 0 ]; then
+  echo "Failures found in the following files:"
+  for FILE in "${FAILURES[@]}"; do
+    echo "  $FILE"
+  done
+  exit 1
+fi
+
+echo "No shellcheck errors."

.github/workflows/shellcheck.yml

@@ -0,0 +1,11 @@
+name: Shellcheck
+on:
+  push:
+  pull_request:
+jobs:
+  shellcheck:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Shellcheck
+        run: .github/shellcheck.sh