Add copyright check to PR checks. (#504)

Added script based on a script from the Firebase iOS repo, with an option to format output for the GitHub log.

Missing copyrights added in a separate PR.

Author: jonsimantov

.github/workflows/checks.yml

@@ -76,3 +76,15 @@ jobs:
             grep -E "error:|warning:|^  parameter" doxygen_errors.txt | sed ':a;N;$!ba;s/\n/%0A/g' | sed 's/^/::error ::DOXYGEN ERRORS:  %0A/'
             exit 1
           fi
+
+  copyright_check:
+    # Check for Google copyright in each file.
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          submodules: false
+      - name: Run check_copyright.sh
+        run: |
+          set -e
+          bash scripts/gha/check_copyright.sh -g

scripts/gha/check_copyright.sh

@@ -0,0 +1,65 @@
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+usage(){
+    echo "Usage: $0 [options]                                                                                          
+ options:                                                                                                              
+   -g          enable github log format"
+}
+
+github_log=0
+IFS=',' # split options on ',' characters                                                                              
+while getopts "hg" opt; do
+    case $opt in
+        h)
+            usage
+            exit 0
+            ;;
+        g)
+	    github_log=1
+            ;;
+        *)
+            echo "unknown parameter"
+            exit 2
+            ;;
+    esac
+done
+
+
+# Check source files for copyright notices
+
+options=(
+  -E  # Use extended regexps
+  -I  # Exclude binary files
+  -L  # Show files that don't have a match
+  'Copyright.*[0-9]{4}.*Google'
+)
+
+result=$(git grep "${options[@]}" -- \
+    '*.'{c,cc,cmake,h,js,m,mm,py,rb,sh,swift} \
+    CMakeLists.txt '**/CMakeLists.txt' \
+    ':(exclude)**/third_party/**' \
+    ':(exclude)**/external/**')
+
+if [[ $result ]]; then
+    if [[ $github_log -eq 1 ]]; then
+	echo -n "::error ::Missing copyright notices in the following files:%0A"
+	# Print all files with %0A instead of newline.
+	echo "$result" | sed ':a;N;$!ba;s/\n/%0A/g'
+    else
+	echo "$result"
+	echo "ERROR: Missing copyright notices in the files above. Please fix."
+    fi
+    exit 1
+fi