Add ruby script.

Author: baijiangliang

linguist.rb

@@ -0,0 +1,16 @@
+require 'rugged'
+require 'linguist'
+require 'json'
+
+# Puts a JSON of language names and corresponding file names.
+def detect_code_files()
+  if ARGV.length != 1 then
+    puts 'Usage: ruby linguist.rb repo_path'
+  end
+  repo_path = ARGV[0]
+  repo = Rugged::Repository.new(repo_path)
+  project = Linguist::Repository.new(repo, repo.head.target_id)
+  puts JSON.generate(project.breakdown_by_file)
+end
+
+detect_code_files()