Add CI workflow to check the license file

.github/workflows/check-license.yml

@@ -0,0 +1,96 @@
+# Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/check-license.md
+name: Check License
+
+env:
+  EXPECTED_LICENSE_FILENAME: LICENSE.txt
+  # SPDX identifier: https://spdx.org/licenses/
+  EXPECTED_LICENSE_TYPE: Apache-2.0
+
+# See: https://docs.github.com/actions/using-workflows/events-that-trigger-workflows
+on:
+  create:
+  push:
+    paths:
+      - ".github/workflows/check-license.ya?ml"
+      # See: https://github.com/licensee/licensee/blob/master/docs/what-we-look-at.md#detecting-the-license-file
+      - "[cC][oO][pP][yY][iI][nN][gG]*"
+      - "[cC][oO][pP][yY][rR][iI][gG][hH][tH]*"
+      - "[lL][iI][cC][eE][nN][cCsS][eE]*"
+      - "[oO][fF][lL]*"
+      - "[pP][aA][tT][eE][nN][tT][sS]*"
+  pull_request:
+    paths:
+      - ".github/workflows/check-license.ya?ml"
+      - "[cC][oO][pP][yY][iI][nN][gG]*"
+      - "[cC][oO][pP][yY][rR][iI][gG][hH][tH]*"
+      - "[lL][iI][cC][eE][nN][cCsS][eE]*"
+      - "[oO][fF][lL]*"
+      - "[pP][aA][tT][eE][nN][tT][sS]*"
+  schedule:
+    # Run periodically to catch breakage caused by external changes.
+    - cron: "0 6 * * WED"
+  workflow_dispatch:
+  repository_dispatch:
+
+jobs:
+  run-determination:
+    runs-on: ubuntu-latest
+    outputs:
+      result: ${{ steps.determination.outputs.result }}
+    steps:
+      - name: Determine if the rest of the workflow should run
+        id: determination
+        run: |
+          RELEASE_BRANCH_REGEX="refs/heads/[0-9]+.[0-9]+.x"
+          # The `create` event trigger doesn't support `branches` filters, so it's necessary to use Bash instead.
+          if [[
+            "${{ github.event_name }}" != "create" ||
+            "${{ github.ref }}" =~ $RELEASE_BRANCH_REGEX
+          ]]; then
+            # Run the other jobs.
+            RESULT="true"
+          else
+            # There is no need to run the other jobs.
+            RESULT="false"
+          fi
+
+          echo "::set-output name=result::$RESULT"
+
+  check-license:
+    needs: run-determination
+    if: needs.run-determination.outputs.result == 'true'
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      - name: Install Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ruby # Install latest version
+
+      - name: Install licensee
+        run: gem install licensee
+
+      - name: Check license file
+        run: |
+          EXIT_STATUS=0
+          # See: https://github.com/licensee/licensee
+          LICENSEE_OUTPUT="$(licensee detect --json --confidence=100)"
+
+          DETECTED_LICENSE_FILE="$(echo "$LICENSEE_OUTPUT" | jq .matched_files[0].filename | tr --delete '\r')"
+          echo "Detected license file: $DETECTED_LICENSE_FILE"
+          if [ "$DETECTED_LICENSE_FILE" != "\"${EXPECTED_LICENSE_FILENAME}\"" ]; then
+            echo "::error file=${DETECTED_LICENSE_FILE}::detected license file $DETECTED_LICENSE_FILE doesn't match expected: $EXPECTED_LICENSE_FILENAME"
+            EXIT_STATUS=1
+          fi
+
+          DETECTED_LICENSE_TYPE="$(echo "$LICENSEE_OUTPUT" | jq .matched_files[0].matched_license | tr --delete '\r')"
+          echo "Detected license type: $DETECTED_LICENSE_TYPE"
+          if [ "$DETECTED_LICENSE_TYPE" != "\"${EXPECTED_LICENSE_TYPE}\"" ]; then
+            echo "::error file=${DETECTED_LICENSE_FILE}::detected license type $DETECTED_LICENSE_TYPE doesn't match expected \"${EXPECTED_LICENSE_TYPE}\""
+            EXIT_STATUS=1
+          fi
+
+          exit $EXIT_STATUS

README.md

@@ -5,6 +5,7 @@
 [![Check Taskfiles status](https://github.com/arduino/arduino-language-server/actions/workflows/check-taskfiles.yml/badge.svg)](https://github.com/arduino/arduino-language-server/actions/workflows/check-taskfiles.yml)
 [![Check Go status](https://github.com/arduino/arduino-language-server/actions/workflows/check-go-task.yml/badge.svg)](https://github.com/arduino/arduino-language-server/actions/workflows/check-go-task.yml)
 [![Check Markdown status](https://github.com/arduino/arduino-language-server/actions/workflows/check-markdown-task.yml/badge.svg)](https://github.com/arduino/arduino-language-server/actions/workflows/check-markdown-task.yml)
+[![Check License status](https://github.com/arduino/arduino-language-server/actions/workflows/check-license.yml/badge.svg)](https://github.com/arduino/arduino-language-server/actions/workflows/check-license.yml)
 
 The **Arduino Language Server** is the tool that powers the autocompletion of the new [Arduino IDE 2][arduino-ide-repo]. It implements the standard [Language Server Protocol](https://microsoft.github.io/language-server-protocol/) so it can be used with other IDEs as well.