diff --git a/Gemfile b/Gemfile
index 6038611d1..270406aab 100644
--- a/Gemfile
+++ b/Gemfile
@@ -86,6 +86,8 @@ gem 'therubyracer', '~> 0.12.1', platforms: [:mri, :rbx]
 gem 'therubyrhino', '~> 1.73.1', platforms: :jruby
 gem 'sitemap_generator'
 
+gem 'codemirror-rails', '~> 4.0'
+
 group :production do
   gem "airbrake", '~> 3.1.2'
   gem 'bluepill', '~> 0.0.60', require: false
diff --git a/Gemfile.lock b/Gemfile.lock
index ece5418b6..c9f60de51 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -122,6 +122,8 @@ GEM
       activesupport (>= 3.0)
     cocaine (0.5.3)
       climate_control (>= 0.0.3, < 1.0)
+    codemirror-rails (4.0)
+      railties (>= 3.0, < 5)
     coderay (1.1.0)
     coffee-rails (4.0.1)
       coffee-script (>= 2.2.0)
@@ -523,6 +525,7 @@ DEPENDENCIES
   capistrano
   capistrano_colors
   charlock_holmes (~> 0.6.9)
+  codemirror-rails (~> 4.0)
   coffee-rails (~> 4.0.1)
   compass-rails (~> 1.1.6)
   creole
diff --git a/app/views/projects/git/blobs/_editor.html.haml b/app/views/projects/git/blobs/_editor.html.haml
index d8d6bb94a..075f2bd80 100644
--- a/app/views/projects/git/blobs/_editor.html.haml
+++ b/app/views/projects/git/blobs/_editor.html.haml
@@ -1,3 +1,6 @@
+= javascript_include_tag 'codemirror_editor'
+= stylesheet_link_tag    'codemirror_editor'
+
 %h3= t("layout.projects.files_in_project")
 .files
   .l= render 'whereami'
@@ -16,3 +19,19 @@
   = submit_tag t('layout.save'), title: t('layout.save'), data: {'disable-with' => t('layout.saving')}
   = t("layout.or")
   = link_to t("layout.cancel"), blob_path(@project, @treeish, @path), class: 'button'
+
+:javascript
+  $(function() {
+    var editor = CodeMirror.fromTextArea(document.getElementById('code'), {
+      lineNumbers: true,
+      mode: '#{@blob.raw_mime_type}'
+    });
+    $(".CodeMirror").resizable({
+      stop: function() { editor.refresh(); },
+      resize: function() {
+        $(".CodeMirror-scroll").height($(this).height());
+        $(".CodeMirror-scroll").width($(this).width());
+        editor.refresh();
+      }
+    });
+  });
\ No newline at end of file
diff --git a/config/environments/production.rb b/config/environments/production.rb
index ce0b0eebc..39258a20b 100644
--- a/config/environments/production.rb
+++ b/config/environments/production.rb
@@ -63,7 +63,9 @@ Rosa::Application.configure do
   config.assets.digest = true
 
   # Precompile additional assets (application.js, application.css, and all non-JS/CSS are already added)
-  config.assets.precompile += %w(login.css login.js reg_session.css tour.css tour.js gollum/editor/langs/*.js moment/ru.js)
+  config.assets.precompile +=
+    %w(login.css login.js reg_session.css tour.css tour.js gollum/editor/langs/*.js moment/ru.js
+       codemirror_editor.js codemirror_editor.css)
 
   # Compress JavaScripts and CSS.
   config.assets.js_compressor = :uglifier
diff --git a/config/environments/staging.rb b/config/environments/staging.rb
index aee5535d7..730cc8e7b 100644
--- a/config/environments/staging.rb
+++ b/config/environments/staging.rb
@@ -62,7 +62,9 @@ Rosa::Application.configure do
   config.assets.digest = true
 
   # Precompile additional assets (application.js, application.css, and all non-JS/CSS are already added)
-  config.assets.precompile += %w(login.css login.js reg_session.css tour.css tour.js gollum/editor/langs/*.js moment/ru.js)
+  config.assets.precompile +=
+    %w(login.css login.js reg_session.css tour.css tour.js gollum/editor/langs/*.js moment/ru.js
+       codemirror_editor.js codemirror_editor.css)
 
   # Compress JavaScripts and CSS.
   config.assets.js_compressor = :uglifier
diff --git a/lib/ext/git/grit.rb b/lib/ext/git/grit.rb
index ca23f9aa0..e484ebeb5 100644
--- a/lib/ext/git/grit.rb
+++ b/lib/ext/git/grit.rb
@@ -43,61 +43,17 @@ module Grit
       end
     end
 
-    # def file_mime_type
-    #   @file_mime_type ||= data.file_type(:mime_type)
-    # end
-    #
-    # def text?
-    #   file_mime_type =~ /^text\// # not binary?
-    # end
-    #
-    # def binary?
-    #   not text? # file_mime_type !~ /^text\//
-    #   # s = data.split(//); ((s.size - s.grep(" ".."~").size) / s.size.to_f) > 0.30 # works only for latin chars
-    # end
-    #
-    # def image?
-    #   mime_type.match(/image/)
-    # end
-
-    DEFAULT_RAW_MIME_TYPE = MIME::Types[DEFAULT_MIME_TYPE].first
-
-    def mime_type_with_class_store
-      set_associated_mimes
-      @associated_mimes.first.simplified
-    end
-    alias_method_chain :mime_type, :class_store
-
     attr_accessor :raw_mime_type
     def raw_mime_type
-      set_associated_mimes
-      @raw_mime_type = @associated_mimes.first || DEFAULT_RAW_MIME_TYPE
-      @raw_mime_type
-    end
-
-    def raw_mime_types
-      set_associated_mimes
-    end
-
-    protected
-
-    # store all associated MIME::Types inside class
-    def set_associated_mimes
-      @associated_mimes ||= []
-      if @associated_mimes.empty?
-        guesses = MIME::Types.type_for(self.name) rescue [DEFAULT_RAW_MIME_TYPE]
-        guesses = [DEFAULT_RAW_MIME_TYPE] if guesses.empty?
-
-        @associated_mimes = guesses.sort{|a,b| mime_sort(a, b)}
+      return @raw_mime_type if @raw_mime_type.present?
+      if mime_type == 'text/rpm-spec'
+        @raw_mime_type = 'text/x-rpm-spec'
+      else
+        @raw_mime_type = Linguist::Language.detect(name, data).try(:lexer).try(:mimetypes).try(:first)
+        @raw_mime_type ||= DEFAULT_MIME_TYPE
+        @raw_mime_type.gsub!('application', 'text')
+        @raw_mime_type
       end
-      @associated_mimes
-    end
-
-    # TODO make more clever function
-    def mime_sort(a,b)
-      return 0 if a.media_type == b.media_type and a.registered? == b.registered?
-      return -1 if a.media_type == 'text' and !a.registered?
-      return 1
     end
   end
 
diff --git a/vendor/assets/javascripts/codemirror_editor.js b/vendor/assets/javascripts/codemirror_editor.js
new file mode 100644
index 000000000..e06c3f412
--- /dev/null
+++ b/vendor/assets/javascripts/codemirror_editor.js
@@ -0,0 +1,78 @@
+//= require codemirror
+
+//= require codemirror/modes/apl
+//= require codemirror/modes/asterisk
+//= require codemirror/modes/clike
+//= require codemirror/modes/clojure
+//= require codemirror/modes/cobol
+//= require codemirror/modes/coffeescript
+//= require codemirror/modes/commonlisp
+//= require codemirror/modes/css
+//= require codemirror/modes/d
+//= require codemirror/modes/diff
+//= require codemirror/modes/dtd
+//= require codemirror/modes/ecl
+//= require codemirror/modes/eiffel
+//= require codemirror/modes/erlang
+//= require codemirror/modes/fortran
+//= require codemirror/modes/gas
+//= require codemirror/modes/gfm
+//= require codemirror/modes/gherkin
+//= require codemirror/modes/go
+//= require codemirror/modes/groovy
+//= require codemirror/modes/haml
+//= require codemirror/modes/haskell
+//= require codemirror/modes/haxe
+//= require codemirror/modes/htmlembedded
+//= require codemirror/modes/htmlmixed
+//= require codemirror/modes/http
+//= require codemirror/modes/jade
+//= require codemirror/modes/javascript
+//= require codemirror/modes/jinja2
+//= require codemirror/modes/julia
+//= require codemirror/modes/livescript
+//= require codemirror/modes/lua
+//= require codemirror/modes/markdown
+//= require codemirror/modes/mirc
+//= require codemirror/modes/mllike
+//= require codemirror/modes/nginx
+//= require codemirror/modes/ntriples
+//= require codemirror/modes/octave
+//= require codemirror/modes/pascal
+//= require codemirror/modes/pegjs
+//= require codemirror/modes/perl
+//= require codemirror/modes/php
+//= require codemirror/modes/pig
+//= require codemirror/modes/properties
+//= require codemirror/modes/puppet
+//= require codemirror/modes/python
+//= require codemirror/modes/q
+//= require codemirror/modes/r
+//= require codemirror/modes/rpm
+//= require codemirror/modes/rst
+//= require codemirror/modes/ruby
+//= require codemirror/modes/rust
+//= require codemirror/modes/sass
+//= require codemirror/modes/scheme
+//= require codemirror/modes/shell
+//= require codemirror/modes/sieve
+//= require codemirror/modes/smalltalk
+//= require codemirror/modes/smarty
+//= require codemirror/modes/smartymixed
+//= require codemirror/modes/solr
+//= require codemirror/modes/sparql
+//= require codemirror/modes/sql
+//= require codemirror/modes/stex
+//= require codemirror/modes/tcl
+//= require codemirror/modes/tiddlywiki
+//= require codemirror/modes/tiki
+//= require codemirror/modes/toml
+//= require codemirror/modes/turtle
+//= require codemirror/modes/vb
+//= require codemirror/modes/vbscript
+//= require codemirror/modes/velocity
+//= require codemirror/modes/verilog
+//= require codemirror/modes/xml
+//= require codemirror/modes/xquery
+//= require codemirror/modes/yaml
+//= require codemirror/modes/z80
diff --git a/vendor/assets/stylesheets/codemirror_editor.scss b/vendor/assets/stylesheets/codemirror_editor.scss
new file mode 100644
index 000000000..6af424b6a
--- /dev/null
+++ b/vendor/assets/stylesheets/codemirror_editor.scss
@@ -0,0 +1,2 @@
+@import "codemirror";
+//@import "codemirror/themes/rubyblue";