implements project languages saving them onto the database

app/models/project.rb

@@ -86,6 +86,18 @@ class Project < ActiveRecord::Base
     end
   end
 
+  # checks if the language main language of the project changed
+  before_save :check_main_language
+  def check_main_language
+    if !repository.empty? && self.changed?
+      language = Linguist::Repository.new(
+        repository.rugged,
+        repository.rugged.head.target_id).language
+
+        self.main_language = language
+    end
+  end
+
   ActsAsTaggableOn.strict_case_match = true
   acts_as_taggable_on :tags
 

db/migrate/20160229193553_add_main_language_to_repository.rb

+class AddMainLanguageToRepository < ActiveRecord::Migration
+  require 'rugged'
+  require 'linguist'
+
+  def up
+    add_column :projects, :main_language, :string, default: nil
+
+    Project.all.each do |project|
+      unless project.repository.empty?
+        language = Linguist::Repository.new(
+          project.repository.rugged,
+          project.repository.rugged.head.target_id).language
+        project.update_attributes(main_language: language)
+      end
+    end
+  end
+
+  def down
+    remove_column :projects, :main_language
+  end
+end