preserve original hooks when initializing

features/initialization.feature

@@ -23,3 +23,13 @@ Feature: Initialization
     | post-checkout      |
     | post-merge         |
     | pre-auto-gc        |
+
+  Scenario: initialization in a repo that already has hooks
+    Given I have a git repository with some commits
+    And the file ".git/hooks/post-commit" contains:
+      """
+      echo "You are awesome"
+      """
+    When I run "git hook init"
+    Then the following folders should exist:
+    | .git/hooks/local/post-commit.d/original |

features/step_definitions/sandbox_steps.rb

@@ -114,6 +114,8 @@
 
 Given /^the file "(.+)" contains:$/ do |filename, content|
   filename.gsub!("$GITTY_ASSETS", ENV["GITTY_ASSETS"])
-  FileUtils.mkdir_p(File.dirname(filename))
-  File.open(filename, "wb") { |f| f << content }
+  in_current_dir do
+    FileUtils.mkdir_p(File.dirname(filename))
+    File.open(filename, "wb") { |f| f << content }
+  end
 end

lib/gitty/commands/init.rb

@@ -21,6 +21,10 @@ def run
     FileUtils.mkdir_p(".git/hooks/local")
 
     CLIENT_HOOKS.each do |hook|
+      if File.exist?(".git/hooks/#{hook}")
+        FileUtils.mkdir_p(".git/hooks/local/#{hook}.d")
+        FileUtils.mv(".git/hooks/#{hook}", ".git/hooks/local/#{hook}.d/original")
+      end
       FileUtils.cp((ASSETS_PATH + "helpers/hookd_wrapper").to_s, ".git/hooks/#{hook}")
       FileUtils.chmod(0755, ".git/hooks/#{hook}")
     end