diff --git a/guides/Rakefile b/guides/Rakefile
index d2591f523c3..ccb42f32739 100644
--- a/guides/Rakefile
+++ b/guides/Rakefile
@@ -1,10 +1,8 @@
 namespace :guides do
-
   desc 'Generate guides (for authors), use ONLY=foo to process just "foo.md"'
   task generate: "generate:html"
 
   namespace :generate do
-
     desc "Generate HTML guides"
     task :html do
       ENV["WARNINGS"] = "1" # authors can't disable this
@@ -18,7 +16,7 @@ namespace :guides do
         abort "Please run `setupkindlerb` to install kindlegen"
       end
       unless `convert` =~ /convert/
-        abort "Please install ImageMagick`"
+        abort "Please install ImageMagick"
       end
       ENV["KINDLE"] = "1"
       Rake::Task["guides:generate:html"].invoke
@@ -33,7 +31,7 @@ namespace :guides do
 
   desc "Show help"
   task :help do
-    puts <<-help
+    puts <<HELP
 
 Guides are taken from the source directory, and the result goes into the
 output directory. Assets are stored under files, and copied to output/files as
@@ -46,8 +44,9 @@ All of these processes are handled via rake tasks, here's a full list of them:
 #{%x[rake -T]}
 Some arguments may be passed via environment variables:
 
-  WARNINGS=1
-    Internal links (anchors) are checked, also detects duplicated IDs.
+  RAILS_VERSION=tag
+    If guides are being generated for a specific Rails version set the Git tag
+    here, otherwise the current SHA1 is going to be used to generate edge guides.
 
   ALL=1
     Force generation of all guides.
@@ -65,15 +64,12 @@ Some arguments may be passed via environment variables:
     Use it when you want to generate translated guides in
     source/<GUIDES_LANGUAGE> folder (such as source/es)
 
-  EDGE=1
-    Indicate generated guides should be marked as edge.
-
 Examples:
-  $ rake guides:generate ALL=1
-  $ rake guides:generate EDGE=1
-  $ rake guides:generate:kindle EDGE=1
+  $ rake guides:generate ALL=1 RAILS_VERSION=v5.1.0
+  $ rake guides:generate ONLY=migrations
+  $ rake guides:generate:kindle
   $ rake guides:generate GUIDES_LANGUAGE=es
-    help
+HELP
   end
 end
 
diff --git a/guides/rails_guides.rb b/guides/rails_guides.rb
index 557d23f78cc..0f611c8f2b8 100644
--- a/guides/rails_guides.rb
+++ b/guides/rails_guides.rb
@@ -1,17 +1,27 @@
-pwd = File.dirname(__FILE__)
-$:.unshift pwd
+$:.unshift __dir__
 
-begin
-  # Guides generation in the Rails repo.
-  as_lib = File.join(pwd, "../activesupport/lib")
-  ap_lib = File.join(pwd, "../actionpack/lib")
+as_lib = File.expand_path("../activesupport/lib", __dir__)
+ap_lib = File.expand_path("../actionpack/lib", __dir__)
+av_lib = File.expand_path("../actionview/lib", __dir__)
 
-  $:.unshift as_lib if File.directory?(as_lib)
-  $:.unshift ap_lib if File.directory?(ap_lib)
-rescue LoadError
-  # Guides generation from gems.
-  gem "actionpack", ">= 3.0"
-end
+$:.unshift as_lib if File.directory?(as_lib)
+$:.unshift ap_lib if File.directory?(ap_lib)
+$:.unshift av_lib if File.directory?(av_lib)
 
 require "rails_guides/generator"
-RailsGuides::Generator.new.generate
+require "active_support/core_ext/object/blank"
+
+env_value = ->(name) { ENV[name].presence }
+env_flag  = ->(name) { "1" == env_value[name] }
+
+version = env_value["RAILS_VERSION"]
+edge    = `git rev-parse HEAD`.strip unless version
+
+RailsGuides::Generator.new(
+  edge:     edge,
+  version:  version,
+  all:      env_flag["ALL"],
+  only:     env_value["ONLY"],
+  kindle:   env_flag["KINDLE"],
+  language: env_value["GUIDES_LANGUAGE"]
+).generate
diff --git a/guides/rails_guides/generator.rb b/guides/rails_guides/generator.rb
index a818ca9d72f..28164a3cb4e 100644
--- a/guides/rails_guides/generator.rb
+++ b/guides/rails_guides/generator.rb
@@ -1,54 +1,3 @@
-# ---------------------------------------------------------------------------
-#
-# This script generates the guides. It can be invoked via the
-# guides:generate rake task within the guides directory.
-#
-# Guides are taken from the source directory, and the resulting HTML goes into the
-# output directory. Assets are stored under files, and copied to output/files as
-# part of the generation process.
-#
-# Some arguments may be passed via environment variables:
-#
-#   WARNINGS
-#     If you are writing a guide, please work always with WARNINGS=1. Users can
-#     generate the guides, and thus this flag is off by default.
-#
-#     Internal links (anchors) are checked. If a reference is broken levenshtein
-#     distance is used to suggest an existing one. This is useful since IDs are
-#     generated by Markdown from headers and thus edits alter them.
-#
-#     Also detects duplicated IDs. They happen if there are headers with the same
-#     text. Please do resolve them, if any, so guides are valid XHTML.
-#
-#   ALL
-#    Set to "1" to force the generation of all guides.
-#
-#   ONLY
-#     Use ONLY if you want to generate only one or a set of guides. Prefixes are
-#     enough:
-#
-#       # generates only association_basics.html
-#       ONLY=assoc rake guides:generate
-#
-#     Separate many using commas:
-#
-#       # generates only association_basics.html and command_line.html
-#       ONLY=assoc,command rake guides:generate
-#
-#     Note that if you are working on a guide generation will by default process
-#     only that one, so ONLY is rarely used nowadays.
-#
-#   GUIDES_LANGUAGE
-#     Use GUIDES_LANGUAGE when you want to generate translated guides in
-#     <tt>source/<GUIDES_LANGUAGE></tt> folder (such as <tt>source/es</tt>).
-#     Ignore it when generating English guides.
-#
-#   EDGE
-#     Set to "1" to indicate generated guides should be marked as edge. This
-#     inserts a badge and changes the preamble of the home page.
-#
-# ---------------------------------------------------------------------------
-
 require "set"
 require "fileutils"
 
@@ -64,46 +13,37 @@ require "rails_guides/levenshtein"
 
 module RailsGuides
   class Generator
-    attr_reader :guides_dir, :source_dir, :output_dir, :edge, :warnings, :all
-
     GUIDES_RE = /\.(?:erb|md)\z/
 
-    def initialize(output = nil)
-      set_flags_from_environment
+    def initialize(edge:, version:, all:, only:, kindle:, language:)
+      @edge     = edge
+      @version  = version
+      @all      = all
+      @only     = only
+      @kindle   = kindle
+      @language = language
 
-      if kindle?
+      if @kindle
         check_for_kindlegen
         register_kindle_mime_types
       end
 
-      initialize_dirs(output)
+      initialize_dirs
       create_output_dir_if_needed
-    end
-
-    def set_flags_from_environment
-      @edge     = ENV["EDGE"]     == "1"
-      @warnings = ENV["WARNINGS"] == "1"
-      @all      = ENV["ALL"]      == "1"
-      @kindle   = ENV["KINDLE"]   == "1"
-      @version  = ENV["RAILS_VERSION"] || "local"
-      @lang     = ENV["GUIDES_LANGUAGE"]
-    end
-
-    def register_kindle_mime_types
-      Mime::Type.register_alias("application/xml", :opf, %w(opf))
-      Mime::Type.register_alias("application/xml", :ncx, %w(ncx))
+      initialize_markdown_renderer
     end
 
     def generate
       generate_guides
       copy_assets
-      generate_mobi if kindle?
+      generate_mobi if @kindle
     end
 
     private
 
-      def kindle?
-        @kindle
+      def register_kindle_mime_types
+        Mime::Type.register_alias("application/xml", :opf, %w(opf))
+        Mime::Type.register_alias("application/xml", :ncx, %w(ncx))
       end
 
       def check_for_kindlegen
@@ -114,29 +54,35 @@ module RailsGuides
 
       def generate_mobi
         require "rails_guides/kindle"
-        out = "#{output_dir}/kindlegen.out"
-        Kindle.generate(output_dir, mobi, out)
+        out = "#{@output_dir}/kindlegen.out"
+        Kindle.generate(@output_dir, mobi, out)
         puts "(kindlegen log at #{out})."
       end
 
       def mobi
-        "ruby_on_rails_guides_#@version%s.mobi" % (@lang.present? ? ".#@lang" : "")
+        mobi  = "ruby_on_rails_guides_#{@version || @edge[0, 7]}"
+        mobi += ".#{@language}" if @language
+        mobi += ".mobi"
       end
 
-      def initialize_dirs(output)
-        @guides_dir = File.join(File.dirname(__FILE__), "..")
-        @source_dir = "#@guides_dir/source/#@lang"
-        @output_dir = if output
-          output
-        elsif kindle?
-          "#@guides_dir/output/kindle/#@lang"
-        else
-          "#@guides_dir/output/#@lang"
-        end.sub(%r</$>, "")
+      def initialize_dirs
+        @guides_dir = File.expand_path("..", __dir__)
+
+        @source_dir  = "#{@guides_dir}/source"
+        @source_dir += "/#{@language}" if @language
+
+        @output_dir  = "#{@guides_dir}/output"
+        @output_dir += "/kindle"       if @kindle
+        @source_dir += "/#{@language}" if @language
       end
 
       def create_output_dir_if_needed
-        FileUtils.mkdir_p(output_dir)
+        FileUtils.mkdir_p(@output_dir)
+      end
+
+      def initialize_markdown_renderer
+        Markdown::Renderer.edge    = @edge
+        Markdown::Renderer.version = @version
       end
 
       def generate_guides
@@ -147,27 +93,27 @@ module RailsGuides
       end
 
       def guides_to_generate
-        guides = Dir.entries(source_dir).grep(GUIDES_RE)
+        guides = Dir.entries(@source_dir).grep(GUIDES_RE)
 
-        if kindle?
-          Dir.entries("#{source_dir}/kindle").grep(GUIDES_RE).map do |entry|
+        if @kindle
+          Dir.entries("#{@source_dir}/kindle").grep(GUIDES_RE).map do |entry|
             next if entry == "KINDLE.md"
             guides << "kindle/#{entry}"
           end
         end
 
-        ENV.key?("ONLY") ? select_only(guides) : guides
+        @only ? select_only(guides) : guides
       end
 
       def select_only(guides)
-        prefixes = ENV["ONLY"].split(",").map(&:strip)
+        prefixes = @only.split(",").map(&:strip)
         guides.select do |guide|
-          guide.start_with?("kindle".freeze, *prefixes)
+          guide.start_with?("kindle", *prefixes)
         end
       end
 
       def copy_assets
-        FileUtils.cp_r(Dir.glob("#{guides_dir}/assets/*"), output_dir)
+        FileUtils.cp_r(Dir.glob("#{@guides_dir}/assets/*"), @output_dir)
       end
 
       def output_file_for(guide)
@@ -179,22 +125,28 @@ module RailsGuides
       end
 
       def output_path_for(output_file)
-        File.join(output_dir, File.basename(output_file))
+        File.join(@output_dir, File.basename(output_file))
       end
 
       def generate?(source_file, output_file)
-        fin  = File.join(source_dir, source_file)
+        fin  = File.join(@source_dir, source_file)
         fout = output_path_for(output_file)
-        all || !File.exist?(fout) || File.mtime(fout) < File.mtime(fin)
+        @all || !File.exist?(fout) || File.mtime(fout) < File.mtime(fin)
       end
 
       def generate_guide(guide, output_file)
         output_path = output_path_for(output_file)
         puts "Generating #{guide} as #{output_file}"
-        layout = kindle? ? "kindle/layout" : "layout"
+        layout = @kindle ? "kindle/layout" : "layout"
 
         File.open(output_path, "w") do |f|
-          view = ActionView::Base.new(source_dir, edge: @edge, version: @version, mobi: "kindle/#{mobi}", lang: @lang)
+          view = ActionView::Base.new(
+            @source_dir,
+            edge:     @edge,
+            version:  @version,
+            mobi:     "kindle/#{mobi}",
+            language: @language
+          )
           view.extend(Helpers)
 
           if guide =~ /\.(\w+)\.erb$/
@@ -202,10 +154,15 @@ module RailsGuides
             # Passing a template handler in the template name is deprecated. So pass the file name without the extension.
             result = view.render(layout: layout, formats: [$1], file: $`)
           else
-            body = File.read(File.join(source_dir, guide))
-            result = RailsGuides::Markdown.new(view, layout).render(body)
+            body = File.read("#{@source_dir}/#{guide}")
+            result = RailsGuides::Markdown.new(
+              view:    view,
+              layout:  layout,
+              edge:    @edge,
+              version: @version
+            ).render(body)
 
-            warn_about_broken_links(result) if @warnings
+            warn_about_broken_links(result)
           end
 
           f.write(result)
@@ -231,7 +188,7 @@ module RailsGuides
         # Footnotes.
         anchors += Set.new(html.scan(/<p\s+class="footnote"\s+id="([^"]+)/).flatten)
         anchors += Set.new(html.scan(/<sup\s+class="footnote"\s+id="([^"]+)/).flatten)
-        return anchors
+        anchors
       end
 
       def check_fragment_identifiers(html, anchors)
diff --git a/guides/rails_guides/markdown.rb b/guides/rails_guides/markdown.rb
index 009e5aff99c..bf2cc82c7c7 100644
--- a/guides/rails_guides/markdown.rb
+++ b/guides/rails_guides/markdown.rb
@@ -4,12 +4,14 @@ require "rails_guides/markdown/renderer"
 
 module RailsGuides
   class Markdown
-    def initialize(view, layout)
-      @view = view
-      @layout = layout
+    def initialize(view:, layout:, edge:, version:)
+      @view          = view
+      @layout        = layout
+      @edge          = edge
+      @version       = version
       @index_counter = Hash.new(0)
-      @raw_header = ""
-      @node_ids = {}
+      @raw_header    = ""
+      @node_ids      = {}
     end
 
     def render(body)
@@ -60,7 +62,8 @@ module RailsGuides
           autolink: true,
           strikethrough: true,
           superscript: true,
-          tables: true)
+          tables: true
+        )
       end
 
       def extract_raw_header_and_body
diff --git a/guides/rails_guides/markdown/renderer.rb b/guides/rails_guides/markdown/renderer.rb
index 8723ee0b4e5..20cbd568c9e 100644
--- a/guides/rails_guides/markdown/renderer.rb
+++ b/guides/rails_guides/markdown/renderer.rb
@@ -1,9 +1,7 @@
 module RailsGuides
   class Markdown
     class Renderer < Redcarpet::Render::HTML
-      def initialize(options = {})
-        super
-      end
+      cattr_accessor :edge, :version
 
       def block_code(code, language)
         <<-HTML
@@ -93,32 +91,30 @@ HTML
         end
 
         def github_file_url(file_path)
-          root, rest = file_path.split("/", 2)
+          tree = version || edge
 
-          case root
-          when "abstract_controller", "action_controller", "action_dispatch"
-            path = ["actionpack", "lib", root, rest].join("/")
-          when "active_support", "active_record", "active_model", "action_view",
-               "action_cable", "action_mailer", "action_pack", "active_job"
-            path = [root.sub("_", ""), "lib", root, rest].join("/")
-          else
-            path = file_path
-          end
+          root = file_path[%r{(.+)/}, 1]
+          path = case root
+                 when "abstract_controller", "action_controller", "action_dispatch"
+                   "actionpack/lib/#{file_path}"
+                 when /\A(action|active)_/
+                   "#{root.sub("_", "")}/lib/#{file_path}"
+                 else
+                   file_path
+                 end
 
-          ["https://github.com/rails/rails/tree", version || "master", path].join("/")
-        end
 
-        def version
-          ENV["RAILS_VERSION"]
+          "https://github.com/rails/rails/tree/#{tree}/#{path}"
         end
 
         def api_link(url)
-          if version && !url.match(/v\d\.\d\.\d/)
-            url.insert(url.index(".org") + 4, "/#{version}")
-            url.sub("http://edgeapi", "http://api") if url.include?("edgeapi")
+          if url =~ %r{http://api\.rubyonrails\.org/v\d+\.}
+            url
+          elsif edge
+            url.sub("api", "edgeapi")
+          else
+            url.sub(/(?<=\.org)/, "/#{version}")
           end
-
-          url
         end
     end
   end
diff --git a/guides/source/_welcome.html.erb b/guides/source/_welcome.html.erb
index f50bcddbe7d..5bd1ea4d222 100644
--- a/guides/source/_welcome.html.erb
+++ b/guides/source/_welcome.html.erb
@@ -1,8 +1,8 @@
-<h2>Ruby on Rails Guides (<%= @edge ? @version[0, 7] : @version %>)</h2>
+<h2>Ruby on Rails Guides (<%= @edge ? @edge[0, 7] : @version %>)</h2>
 
 <% if @edge %>
 <p>
-  These are <b>Edge Guides</b>, based on the current <a href="https://github.com/rails/rails/tree/<%= @version %>">master</a> branch.
+  These are <b>Edge Guides</b>, based on <a href="https://github.com/rails/rails/tree/<%= @edge %>">master@<%= @edge[0, 7] %></a>.
 </p>
 <p>
   If you are looking for the ones for the stable version, please check
diff --git a/guides/source/kindle/rails_guides.opf.erb b/guides/source/kindle/rails_guides.opf.erb
index 547abcbc192..63eeb007d73 100644
--- a/guides/source/kindle/rails_guides.opf.erb
+++ b/guides/source/kindle/rails_guides.opf.erb
@@ -5,7 +5,7 @@
   <meta name="cover" content="cover" />
   <dc-metadata xmlns:dc="http://purl.org/dc/elements/1.1/">
 
-  	<dc:title>Ruby on Rails Guides (<%= @version %>)</dc:title>
+       <dc:title>Ruby on Rails Guides (<%= @version || "master@#{@edge[0, 7]}" %>)</dc:title>
 
   	<dc:language>en-us</dc:language>
   	<dc:creator>Ruby on Rails</dc:creator>