diff --git a/bin/git-evolution b/bin/git-evolution
index e929d18..8419383 100755
--- a/bin/git-evolution
+++ b/bin/git-evolution
@@ -2,4 +2,4 @@
 
 require 'git_evolution'
 
-GitEvolution.new.run(ARGV)
+GitEvolution.run(ARGV)
diff --git a/bin/git_evolution b/bin/git_evolution
index e929d18..8419383 100755
--- a/bin/git_evolution
+++ b/bin/git_evolution
@@ -2,4 +2,4 @@
 
 require 'git_evolution'
 
-GitEvolution.new.run(ARGV)
+GitEvolution.run(ARGV)
diff --git a/git_evolution.gemspec b/git_evolution.gemspec
index 525003f..aa91654 100644
--- a/git_evolution.gemspec
+++ b/git_evolution.gemspec
@@ -20,4 +20,5 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency 'bundler', '~> 1.7'
   spec.add_development_dependency 'rake', '~> 10.0'
+  spec.add_development_dependency 'rugged', '~> 0.21.4'
 end
diff --git a/lib/git_evolution.rb b/lib/git_evolution.rb
index ef3b9be..26d6064 100644
--- a/lib/git_evolution.rb
+++ b/lib/git_evolution.rb
@@ -1,10 +1,14 @@
-class GitEvolution
-  def run(args)
+require_relative './git_evolution/initialize.rb'
+
+module GitEvolution
+  def self.run(args)
     start_line = args[0]
     end_line = args[1]
     file = args[2]
 
-    results = `git --no-pager log -L#{start_line},#{end_line}:#{file} --follow #{file}`
+    repo = Repository.new(File.dirname(File.expand_path(file)))
+
+    results = repo.line_history(start_line, end_line, file)
 
     commit_shas = results.scan(/^commit ([0-9a-f]{40})/)
     commit_shas = commit_shas.flatten
diff --git a/lib/git_evolution/initialize.rb b/lib/git_evolution/initialize.rb
new file mode 100644
index 0000000..f34a4c9
--- /dev/null
+++ b/lib/git_evolution/initialize.rb
@@ -0,0 +1,3 @@
+require 'rugged'
+
+Dir.glob(File.dirname(__FILE__) + '/**/*.rb') { |file| require file  }
diff --git a/lib/git_evolution/repository.rb b/lib/git_evolution/repository.rb
new file mode 100644
index 0000000..8ae3e56
--- /dev/null
+++ b/lib/git_evolution/repository.rb
@@ -0,0 +1,17 @@
+module GitEvolution
+  class Repository
+    def initialize(directory_name)
+      @git_repo = Rugged::Repository.discover(File.expand_path(directory_name))
+    end
+
+    def dir
+      @git_repo.workdir
+    end
+
+    def line_history(start_line, end_line, file)
+      Dir.chdir(dir) do
+        return `git --no-pager log -L#{start_line},#{end_line}:#{file} --follow #{file}`
+      end
+    end
+  end
+end
diff --git a/lib/git_evolution/version.rb b/lib/git_evolution/version.rb
index 4d11ed1..e35259f 100644
--- a/lib/git_evolution/version.rb
+++ b/lib/git_evolution/version.rb
@@ -1,3 +1,3 @@
-class GitEvolution
+module GitEvolution
   VERSION = '0.0.1'
 end
diff --git a/spec/git_evolution/repository_spec.rb b/spec/git_evolution/repository_spec.rb
new file mode 100644
index 0000000..2a73741
--- /dev/null
+++ b/spec/git_evolution/repository_spec.rb
@@ -0,0 +1,24 @@
+require 'spec_helper'
+
+RSpec.describe GitEvolution::Repository do
+  describe '.new' do
+    context 'valid repository directory' do
+      before(:each) { RepositoryHelper.create_repository }
+      after(:each) { RepositoryHelper.delete_repository }
+
+      it 'detects repository' do
+        repo = described_class.new(RepositoryHelper.repository_dir)
+        expect(repo.dir).to eq(RepositoryHelper.repository_dir)
+      end
+    end
+
+    context 'invalid repository directory' do
+      let!(:tmp_dir) { Dir.mktmpdir }
+      after { FileUtils.rm_r(tmp_dir) }
+
+      it 'detects no repository' do
+        expect { described_class.new(tmp_dir) }.to raise_error(Rugged::RepositoryError)
+      end
+    end
+  end
+end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
new file mode 100644
index 0000000..71bf98c
--- /dev/null
+++ b/spec/spec_helper.rb
@@ -0,0 +1,8 @@
+$LOAD_PATH.unshift File.expand_path('../lib', __FILE__)
+
+Bundler.require(:test)
+Bundler.require(:development)
+
+Dir.glob(Dir.pwd + '/spec/support/**/*.rb') { |file| require file }
+
+require 'git_evolution/initialize'
diff --git a/spec/support/repository_helper.rb b/spec/support/repository_helper.rb
new file mode 100644
index 0000000..cb4f0ff
--- /dev/null
+++ b/spec/support/repository_helper.rb
@@ -0,0 +1,16 @@
+module RepositoryHelper
+  module_function
+
+  def create_repository
+    @tmp_git_dir = Dir.mktmpdir
+    Rugged::Repository.init_at(@tmp_git_dir)
+  end
+
+  def delete_repository
+    FileUtils.rm_r(@tmp_git_dir)
+  end
+
+  def repository_dir
+    File.realpath(@tmp_git_dir) + '/'
+  end
+end