Add 'rake build:watch'

README.md

@@ -3,7 +3,7 @@
 </p>
 
 This repository contains the source code of
-[al-quran.reflectslight.io](https://al-quran.reflectslight.io), 
+[al-quran.reflectslight.io](https://al-quran.reflectslight.io),&nbsp;
 a static website for reading The Quran. After the
 website is built, the build directory consists
 of HTML, CSS, JavaScript and other static assets
@@ -34,8 +34,12 @@ __2. Install Ruby, and NodeJS packages__
 
 __3. Build website__
 
+    # Build once
     rake build
 
+    # Build whenever a change is detected
+    rake build:watch
+
 __4. Start server on localhost__
 
     rake server

Rakefile.rb

@@ -7,21 +7,30 @@ require "yaml"
 build_dir = Ryo.from(YAML.load_file("./nanoc.yaml")).output_dir
 
 namespace :nanoc do
-  desc "Compile the website"
   task :compile do
     ENV["SASS_PATH"] = "./src/css/"
     sh "bundle exec nanoc co"
   end
 
-  desc "Delete the build directory"
   task :clean do
     sh "rm -rf #{build_dir}"
   end
+
+  task watch: [:compile] do
+    require "listen"
+    Listen.to File.join(Dir.getwd, "src"), force_polling: true do
+      sh "rake build"
+    end.start
+    sleep
+  end
 end
 
 desc "Build the website"
 task build: "nanoc:compile"
 
+desc "Trigger a build when src/ is modified"
+task "build:watch" => "nanoc:watch"
+
 desc "Clean the build directory"
 task clean: "nanoc:clean"