Trigger post-receive hoooks when commits are made by GitLab

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/services/post_commit_service.rb

 class PostCommitService < BaseService
+  include Gitlab::Popen
+
+  attr_reader :changes
+
   def execute(sha, branch)
     commit = repository.commit(sha)
     full_ref = 'refs/heads/' + branch
     old_sha = commit.parent_id || Gitlab::Git::BLANK_SHA
-    GitPushService.new.execute(project, current_user, old_sha, sha, full_ref)
+
+    @changes = "#{old_sha} #{sha} #{full_ref}"
+    post_receive(@changes, repository.path_to_repo)
+  end
+
+  private
+
+  def post_receive(changes, repo_path)
+    hook = hook_file('post-receive', repo_path)
+    return true if hook.nil?
+    call_receive_hook(hook, changes) ? true : false
+  end
+
+  def call_receive_hook(hook, changes)
+    # function  will return true if succesful
+    exit_status = false
+
+    vars = {
+      'GL_ID' => Gitlab::ShellEnv.gl_id(current_user),
+      'PWD' => repository.path_to_repo
+    }
+
+    options = {
+      chdir: repository.path_to_repo
+    }
+
+    # we combine both stdout and stderr as we don't know what stream
+    # will be used by the custom hook
+    Open3.popen2e(vars, hook, options) do |stdin, stdout_stderr, wait_thr|
+      exit_status = true
+      stdin.sync = true
+
+      # in git, pre- and post- receive hooks may just exit without
+      # reading stdin. We catch the exception to avoid a broken pipe
+      # warning
+      begin
+        # inject all the changes as stdin to the hook
+        changes.lines do |line|
+          stdin.puts (line)
+        end
+      rescue Errno::EPIPE
+      end
+
+      # need to close stdin before reading stdout
+      stdin.close
+
+      # only output stdut_stderr if scripts doesn't return 0
+      unless wait_thr.value == 0
+        exit_status = false
+        stdout_stderr.each_line { |line| puts line }
+      end
+    end
+
+    exit_status
+  end
+
+  def hook_file(hook_type, repo_path)
+    hook_path = File.join(repo_path.strip, 'hooks')
+    hook_file = "#{hook_path}/#{hook_type}"
+    hook_file if File.exist?(hook_file)
   end
 end