uses Dir.chdir instead of --git-dir

It is hard to handle special characters appropriately to maintain --git-dir option dynamically.
So repository directory should be given as current directory, instead of command line option.
Dir.chdir-with-block takes effect only in the trailing block.

Author: yuba

app/controllers/github_hook_controller.rb

@@ -52,16 +52,18 @@ def exec(command)
     logfile.unlink
   end
 
-  def git_command(command, repository)
-    GIT_BIN + " --git-dir=\"#{repository.url}\" #{command}"
+  def git_command(command)
+    GIT_BIN + " #{command}"
   end
 
   # Fetches updates from the remote repository
   def update_repository(repository)
-    command = git_command('fetch origin', repository)
-    if exec(command)
-      command = git_command("fetch origin \"+refs/heads/*:refs/heads/*\"", repository)
-      exec(command)
+    Dir.chdir(repository.url) do
+      command = git_command('fetch origin')
+      if exec(command)
+        command = git_command("fetch origin \"+refs/heads/*:refs/heads/*\"")
+        exec(command)
+      end
     end
   end