Set push data object kind in PushDataBuilder.

app/services/create_tag_service.rb

@@ -40,9 +40,7 @@ class CreateTagService < BaseService
   end
 
   def create_push_data(project, user, tag)
-    data = Gitlab::PushDataBuilder.
+    Gitlab::PushDataBuilder.
       build(project, user, Gitlab::Git::BLANK_SHA, tag.target, "#{Gitlab::Git::TAG_REF_PREFIX}#{tag.name}", [])
-    data[:object_kind] = "tag_push"
-    data
   end
 end

app/services/git_tag_push_service.rb

@@ -16,8 +16,6 @@ class GitTagPushService
   private
 
   def create_push_data(oldrev, newrev, ref)
-    data = Gitlab::PushDataBuilder.build(project, user, oldrev, newrev, ref, [])
-    data[:object_kind] = "tag_push"
-    data
+    Gitlab::PushDataBuilder.build(project, user, oldrev, newrev, ref, [])
   end
 end

lib/gitlab/push_data_builder.rb

@@ -28,9 +28,10 @@ module Gitlab
         # Get latest 20 commits ASC
         commits_limited = commits.last(20)
 
+        type = Gitlab::Git.tag_ref?(ref) ? "tag_push" : "push"
         # Hash to be passed as post_receive_data
         data = {
-          object_kind: "push",
+          object_kind: type,
           before: oldrev,
           after: newrev,
           ref: ref,