Merge branch '21040-blob-as-tag' into 'master'

Fix Projects::UpdateMirrorService to allow tags pointing to blob objects

After the release of https://gitlab.com/gitlab-org/gitlab_git/merge_requests/103 we changed the way we return the target of tag objects, now it's a Commit object if there is some and nil in any other case, like when a tag points to a Blob object.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/21040

See merge request !673

CHANGELOG-EE

@@ -15,6 +15,7 @@ v 8.11.0 (unreleased)
   - [Elastic] Significant improvement of global search performance
   - [Fix] Push rules check existing commits in some cases
   - [ES] Limit amount of retries for sidekiq jobs
+  - Fix Projects::UpdateMirrorService to allow tags pointing to blob objects
 
 v 8.10.7
   - No EE-specific changes

app/services/projects/update_mirror_service.rb

@@ -62,14 +62,14 @@ module Projects
     end
 
     def update_tags(&block)
-      old_tags = repository.tags.each_with_object({}) { |tag, tags| tags[tag.name] = tag }
+      old_tags = repository_tags_with_target.each_with_object({}) { |tag, tags| tags[tag.name] = tag }
 
       fetch_result = block.call
       return fetch_result unless fetch_result
 
       repository.expire_tags_cache
 
-      tags = repository.tags
+      tags = repository_tags_with_target
 
       tags.each do |tag|
         old_tag = old_tags[tag.name]
@@ -92,5 +92,11 @@ module Projects
 
       fetch_result
     end
+
+    # In Git is possible to tag blob objects, and those blob objects don't point to a Git commit so those tags
+    # have no target.
+    def repository_tags_with_target
+      repository.tags.select(&:target)
+    end
   end
 end

spec/services/projects/update_mirror_service_spec.rb

@@ -26,6 +26,15 @@ describe Projects::UpdateMirrorService do
 
         expect(project.repository.tag_names).to include('new-tag')
       end
+
+      it "only invokes GitTagPushService for tags pointing to commits" do
+        stub_fetch_mirror(project)
+
+        expect(GitTagPushService).to receive(:new).
+          with(project, project.owner, hash_including(ref: 'refs/tags/new-tag')).and_return(double(execute: true))
+
+        described_class.new(project, project.owner).execute
+      end
     end
 
     describe "updating branches" do
@@ -112,5 +121,8 @@ describe Projects::UpdateMirrorService do
 
     # New tag
     rugged.references.create('refs/tags/new-tag', masterrev)
+
+    # New tag that point to a blob
+    rugged.references.create('refs/tags/new-tag-on-blob', 'c74175afd117781cbc983664339a0f599b5bb34e')
   end
 end