Merge branch 'dm-git-hook-popen' into 'master'

Only set cwd on the newly spawned process, instead of the current one

See merge request gitlab-org/gitlab-ce!16958

lib/gitlab/git/hook.rb

@@ -82,15 +82,21 @@ module Gitlab
       end
 
       def call_update_hook(gl_id, gl_username, oldrev, newrev, ref)
-        Dir.chdir(repo_path) do
         env = {
           'GL_ID' => gl_id,
-            'GL_USERNAME' => gl_username
+          'GL_USERNAME' => gl_username,
+          'PWD' => repo_path
+        }
+
+        options = {
+          chdir: repo_path
         }
-          stdout, stderr, status = Open3.capture3(env, path, ref, oldrev, newrev)
+
+        args = [ref, oldrev, newrev]
+
+        stdout, stderr, status = Open3.capture3(env, path, *args, options)
         [status.success?, (stderr.presence || stdout).gsub(/\R/, "<br>").html_safe]
       end
-      end
 
       def retrieve_error_message(stderr, stdout)
         err_message = stderr.read