Update ReleasesImporter to ignore nil/dup tags

Update LegacyBulkInsert to allow ignoring
conflicts on multiple keys / indexes

lib/gitlab/github_import/importer/releases_importer.rb

@@ -21,10 +21,12 @@ module Gitlab
         end
 
         def already_imported?(release)
-          existing_tags.include?(release.tag_name)
+          existing_tags.include?(release.tag_name) || release.tag_name.nil?
         end
 
         def build(release)
+          existing_tags.add(release.tag_name)
+
           {
             name: release.name,
             tag: release.tag_name,

lib/gitlab/legacy_github_import/release_formatter.rb

@@ -25,7 +25,7 @@ module Gitlab
       end
 
       def valid?
-        !raw_data.draft
+        !raw_data.draft && raw_data.tag_name.present?
       end
     end
   end

spec/lib/gitlab/github_import/importer/releases_importer_spec.rb

@@ -52,6 +52,12 @@ RSpec.describe Gitlab::GithubImport::Importer::ReleasesImporter do
 
       expect { importer.execute }.to change { Release.count }.by(1)
     end
+
+    it 'is idempotent' do
+      allow(importer).to receive(:each_release).and_return([github_release])
+      expect { importer.execute }.to change { Release.count }.by(1)
+      expect { importer.execute }.to change { Release.count }.by(0) # Idempotency check
+    end
   end
 
   describe '#build_releases' do
@@ -79,6 +85,24 @@ RSpec.describe Gitlab::GithubImport::Importer::ReleasesImporter do
 
       expect(release[:description]).to eq('Release for tag 1.0')
     end
+
+    it 'does not create releases that have a NULL tag' do
+      null_tag_release = double(
+        name: 'NULL Test',
+        tag_name: nil
+      )
+
+      expect(importer).to receive(:each_release).and_return([null_tag_release])
+      expect(importer.build_releases).to be_empty
+    end
+
+    it 'does not create duplicate release tags' do
+      expect(importer).to receive(:each_release).and_return([github_release, github_release])
+
+      releases = importer.build_releases
+      expect(releases.length).to eq(1)
+      expect(releases[0][:description]).to eq('This is my release')
+    end
   end
 
   describe '#build' do

spec/lib/gitlab/legacy_github_import/release_formatter_spec.rb

@@ -63,5 +63,13 @@ RSpec.describe Gitlab::LegacyGithubImport::ReleaseFormatter do
         expect(release.valid?).to eq false
       end
     end
+
+    context 'when release has NULL tag' do
+      let(:raw_data) { double(base_data.merge(tag_name: '')) }
+
+      it 'returns false' do
+        expect(release.valid?).to eq false
+      end
+    end
   end
 end