Add cursory first-line check of test files

Author: Michael Lyons

syntax-tests.sh

@@ -153,9 +153,14 @@ link_additional_packages
 create_dummy_syntaxes
 
 echo "::group::Checking syntax test filenames"
-for path in $(find . -iname syntax_test* | grep -v '/syntax_test_'); do
+for path in $(find . -iname syntax_test*); do
     file="${path/$packages\/$INPUT_PACKAGE_NAME/$INPUT_PACKAGE_ROOT}"
-    echo "::warning file=$file::Syntax test files must begin with 'syntax_test_'"
+    if echo "$file" | grep -v '/syntax_test_'; then
+        echo "::warning file=$file::Syntax test filenames must begin with 'syntax_test_'"
+    fi
+    if head -n 1 "$path" | grep -vEq '.+\bSYNTAX TEST\b.+".+\.(sublime-syntax|tmLanguage)"'; then
+        echo "::warning file=$file::Syntax test file format at https://www.sublimetext.com/docs/syntax.html#testing"
+    fi
 done
 echo '::endgroup::'