build: squash: switch back to reusable workflow

.github/workflows/shellcheck.yml

@@ -0,0 +1,83 @@
+# This is a reusable workflow for running ShellCheck,
+# a linter for shell scripts (https://shellcheck.net).
+
+# For more context, see:
+# https://github.com/openedx/.github/blob/master/docs/decisions/0001-shellcheck.rst
+
+name: ShellCheck
+
+on: 
+  workflow_call:
+    inputs:
+
+      root-dirs:
+        type: string
+        required: true
+        description: |
+          Directories to search for .sh files, space-separated, each relative
+          to the root of the repository. Directories containing spaces or other
+          Bash delimiters must be wrapped in single quotes.
+    
+      shellcheck-version:
+        type: string
+        required: false
+        default: "v0.9.0"
+        description:
+          ShellCheck version to install.
+          Must be a tag or branch of https://github.com/koalaman/shellcheck.
+          By default, the upstream action will use a reasonable, stable shellcheck version,
+          which will be updated over time as new stable ShellCheck versions come out.
+          If you want your repositoriy's build to be totally deterministic, though, then
+          override with a specific version pin here, and manage updates ShellCheck yourself.
+
+      # OPTIONAL:
+      shellcheck-options:
+        type: string
+        required: false
+        default: ""
+        description: |
+          Command-line options to forward to shellcheck.
+          For details of available options, run "shellcheck --help."
+
+jobs:
+  shellcheck:
+    runs-on: ubuntu-latest
+
+    steps:
+
+    - name: Download & unpack ShellCheck
+        wget -qO- "https://github.com/koalaman/shellcheck/releases/download/${{ inputs.shellcheck-version }}/shellcheck-${{ inputs.shellcheck-version }}.linux.x86_64.tar.xz" | tar -xJ
+
+    - name: Install ShellCheck
+      run: sudo cp "shellcheck-${{ inputs.shellcheck-version }}/shellcheck" /usr/bin
+
+    - name: Show ShellCheck version
+      run: shellcheck -V
+
+    - name: Check out repository branch
+      uses: actions/checkout@v3
+
+    - name: Ensure that at least one script will be checked
+      run: |
+        if [[ -z "$(find ${{ inputs.root-dirs }} -name '*.sh')" ]] ; then
+          echo "::error::Error: No .sh files found within any of the root-dirs: ${{ inputs.root-dirs }}"
+          exit 1
+        fi 
+
+    - name: Print helpful information
+      run: |
+        echo "The following shell scripts will be checked:"
+        find ${{ inputs.root-dirs }} -name '*.sh'
+        echo
+        echo "If ShellCheck passes, the next step will have no output."
+        echo "If ShellCheck fails, you should see a list of violations."
+        echo "Each violation type has an SCXXXX code which can be looked up at https://www.shellcheck.net/wiki/SCXXXX"
+        echo "We recommend that you try to resolve any violations."
+        echo "In the case where resolving the violation doesn't make sense, you can use directives (https://www.shellcheck.net/wiki/Directive) to ignore a single violation instance or an entire shell script."
+        echo
+
+    # This step is intentionally a big one-line command so that
+    # devs can easily copy it and run it on their own machine.
+    - name: Run ShellCheck
+      run: find ${{ inputs.root-dirs }} -name '*.sh' -print0 | xargs -0 shellcheck ${{ inputs.shellcheck-options }}
+