Extract strip_color_codes into Utils module

This helper seems generic enough that it will probably become useful in
future.

Author: sds

lib/overcommit/hook/pre_commit/html_hint.rb

@@ -5,7 +5,7 @@ module Overcommit::Hook::PreCommit
   class HtmlHint < Base
     def run
       result = execute(command + applicable_files)
-      output = strip_color_codes(result.stdout.chomp)
+      output = Overcommit::Utils.strip_color_codes(result.stdout.chomp)
 
       message_groups = output.split("\n\n")[0..-2]
       message_groups.map do |group|
@@ -17,11 +17,5 @@ def run
         )
       end.flatten
     end
-
-    private
-
-    def strip_color_codes(output)
-      output.gsub(/\e\[(\d+)(;\d+)*m/, '')
-    end
   end
 end

lib/overcommit/utils.rb

@@ -72,6 +72,16 @@ def git_dir(repo_dir = repo_root)
           end
       end
 
+      # Remove ANSI escape sequences from a string.
+      #
+      # This is useful for stripping colorized output from external tools.
+      #
+      # @param text [String]
+      # @return [String]
+      def strip_color_codes(text)
+        text.gsub(/\e\[(\d+)(;\d+)*m/, '')
+      end
+
       # Shamelessly stolen from:
       # stackoverflow.com/questions/1509915/converting-camel-case-to-underscore-case-in-ruby
       def snake_case(str)

spec/overcommit/utils_spec.rb

@@ -77,6 +77,28 @@
     end
   end
 
+  describe '.strip_color_codes' do
+    subject { described_class.strip_color_codes(text) }
+
+    context 'with an empty string' do
+      let(:text) { '' }
+
+      it { should == '' }
+    end
+
+    context 'with a string with no escape sequences' do
+      let(:text) { 'A normal string' }
+
+      it { should == text }
+    end
+
+    context 'with a string with escape sequences' do
+      let(:text) { "A \e[31mcolored string\e[39m" }
+
+      it { should == 'A colored string' }
+    end
+  end
+
   describe '.snake_case' do
     it 'converts camel case to underscores' do
       described_class.snake_case('HelloWorld').should == 'hello_world'