Add pre commit hook for fasterer

config/default.yml

@@ -247,6 +247,11 @@ PreCommit:
     description: 'Check for file execute permissions'
     quiet: true
 
+  Fasterer:
+    enabled: false
+    description: 'Suggest some speed improvements'
+    required_executable: 'fasterer'
+
   ForbiddenBranches:
     enabled: false
     description: 'Check for commit to forbidden branch'

lib/overcommit/hook/pre_commit/fasterer.rb

@@ -0,0 +1,23 @@
+module Overcommit::Hook::PreCommit
+  # Runs `fasterer` against any modified Ruby files.
+  #
+  # @see https://github.com/DamirSvrtan/fasterer
+  class Fasterer < Base
+    def run
+      result = execute(command)
+      output = result.stdout
+
+      if extract_offense_num(output) == 0
+        :pass
+      else
+        return [:warn, output]
+      end
+    end
+
+    private
+
+    def extract_offense_num(raw_output)
+      raw_output.scan(/(\d+) offense detected/).flatten.map(&:to_i).inject(0, :+)
+    end
+  end
+end

spec/overcommit/hook/pre_commit/fasterer_spec.rb

@@ -0,0 +1,69 @@
+require 'spec_helper'
+
+describe Overcommit::Hook::PreCommit::Fasterer do
+  let(:config)  { Overcommit::ConfigurationLoader.default_configuration }
+  let(:context) { double('context') }
+  subject { described_class.new(config, context) }
+
+  before do
+    subject.stub(:applicable_files).and_return(%w[file1.js file2.js])
+  end
+
+  around do |example|
+    repo do
+      example.run
+    end
+  end
+
+  before do
+    subject.stub(:execute).with(%w[fasterer]).and_return(result)
+  end
+
+  context 'and has 2 suggestions for speed improvement' do
+    let(:result) do
+      double(
+        success?: false,
+        stdout: <<-EOF
+spec/models/product_spec.rb
+Using each_with_index is slower than while loop. Occurred at lines: 52.
+
+1 files inspected, 1 offense detected
+spec/models/book_spec.rb
+Using each_with_index is slower than while loop. Occurred at lines: 32.
+
+1 files inspected, 1 offense detected
+spec/models/blog_spec.rb
+Using each_with_index is slower than while loop. Occurred at lines: 12.
+
+2 files inspected, 0 offense detected
+      EOF
+      )
+    end
+
+    it { should warn }
+  end
+
+  context 'and has single suggestion for speed improvement' do
+    let(:result) do
+      double(
+        success?: false,
+        stdout: <<-EOF
+spec/models/product_spec.rb
+Using each_with_index is slower than while loop. Occurred at lines: 52.
+
+1 files inspected, 1 offense detected
+      EOF
+      )
+    end
+
+    it { should warn }
+  end
+
+  context 'and does not have any suggestion' do
+    let(:result) do
+      double(success?: true, stdout: '55 files inspected, 0 offenses detected')
+    end
+
+    it { should pass }
+  end
+end