Fix wiki repositories with wrong HEAD

In this commit we ensure to fix HEAD in wiki
repositories when it pointes to the wrong branch.

Changelog: fixed

app/models/wiki.rb

@@ -87,7 +87,8 @@ class Wiki
   end
 
   def create_wiki_repository
-    change_head_to_default_branch if repository.create_if_not_exists
+    repository.create_if_not_exists
+    change_head_to_default_branch
 
     raise CouldNotCreateWikiError unless repository_exists?
   rescue StandardError => err
@@ -249,7 +250,7 @@ class Wiki
 
   override :default_branch
   def default_branch
-    super || wiki.class.default_ref(container)
+    super || Gitlab::Git::Wiki.default_ref(container)
   end
 
   def wiki_base_path
@@ -323,6 +324,12 @@ class Wiki
   end
 
   def change_head_to_default_branch
+    # If the wiki has commits in the 'HEAD' branch means that the current
+    # HEAD is pointing to the right branch. If not, it could mean that either
+    # the repo has just been created or that 'HEAD' is pointing
+    # to the wrong branch and we need to rewrite it
+    return if repository.raw_repository.commit_count('HEAD') != 0
+
     repository.raw_repository.write_ref('HEAD', "refs/heads/#{default_branch}")
   end
 end

app/services/wikis/create_attachment_service.rb

@@ -21,7 +21,11 @@ module Wikis
     end
 
     def create_commit!
+      wiki.create_wiki_repository
+
       commit_result(create_transformed_commit(@file_content))
+    rescue Wiki::CouldNotCreateWikiError
+      raise_error("Error creating the wiki repository")
     end
 
     private

ee/spec/models/group_wiki_spec.rb

@@ -19,6 +19,7 @@ RSpec.describe GroupWiki do
 
         # Don't actually create the repository, because the storage shard doesn't exist.
         expect(subject.repository).to receive(:create_if_not_exists)
+        expect(subject).to receive(:change_head_to_default_branch)
         allow(subject).to receive(:repository_exists?).and_return(true)
 
         expect(subject).to receive(:track_wiki_repository).with(shard)

spec/support/shared_examples/models/wiki_shared_examples.rb

@@ -575,18 +575,21 @@ RSpec.shared_examples 'wiki model' do
   end
 
   describe '#create_wiki_repository' do
+    let(:head_path) { Rails.root.join(TestEnv.repos_path, "#{wiki.disk_path}.git", 'HEAD') }
+    let(:default_branch) { 'foo' }
+
+    before do
+      allow(Gitlab::CurrentSettings).to receive(:default_branch_name).and_return(default_branch)
+    end
+
     subject { wiki.create_wiki_repository }
 
     context 'when repository is not created' do
       let(:wiki_container) { wiki_container_without_repo }
-      let(:head_path) { Rails.root.join(TestEnv.repos_path, "#{wiki.disk_path}.git", 'HEAD') }
-      let(:default_branch) { 'foo' }
 
       it 'changes the HEAD reference to the default branch' do
         expect(wiki.empty?).to eq true
 
-        allow(Gitlab::CurrentSettings).to receive(:default_branch_name).and_return(default_branch)
-
         subject
 
         expect(File.read(head_path).squish).to eq "ref: refs/heads/#{default_branch}"
@@ -596,23 +599,36 @@ RSpec.shared_examples 'wiki model' do
     context 'when repository is empty' do
       let(:wiki_container) { wiki_container_without_repo }
 
-      it 'does nothing' do
+      it 'changes the HEAD reference to the default branch' do
         wiki.repository.create_if_not_exists
-
-        expect(wiki).not_to receive(:change_head_to_default_branch)
+        wiki.repository.raw_repository.write_ref('HEAD', 'refs/heads/bar')
 
         subject
+
+        expect(File.read(head_path).squish).to eq "ref: refs/heads/#{default_branch}"
       end
     end
 
     context 'when repository is not empty' do
-      it 'does nothing' do
+      before do
         wiki.create_page('index', 'test content')
+      end
 
-        expect(wiki).not_to receive(:change_head_to_default_branch)
+      it 'does nothing when HEAD points to the right branch' do
+        expect(wiki.repository.raw_repository).not_to receive(:write_ref)
 
         subject
       end
+
+      context 'when HEAD points to the wrong branch' do
+        it 'rewrites HEAD with the right branch' do
+          wiki.repository.raw_repository.write_ref('HEAD', 'refs/heads/bar')
+
+          subject
+
+          expect(File.read(head_path).squish).to eq "ref: refs/heads/#{default_branch}"
+        end
+      end
     end
   end
 end

spec/support/shared_examples/services/wikis/create_attachment_service_shared_examples.rb

@@ -25,6 +25,25 @@ RSpec.shared_examples 'Wikis::CreateAttachmentService#execute' do |container_typ
     container.add_developer(user)
   end
 
+  context 'creates wiki repository if it does not exist' do
+    let(:container) { create(container_type) } # rubocop:disable Rails/SaveBang
+
+    it 'creates wiki repository' do
+      expect { service.execute }.to change { container.wiki.repository.exists? }.to(true)
+    end
+
+    context 'if an error is raised creating the repository' do
+      it 'catches error and return gracefully' do
+        allow(container.wiki).to receive(:repository_exists?).and_return(false)
+
+        result = service.execute
+
+        expect(result[:status]).to eq :error
+        expect(result[:message]).to eq 'Error creating the wiki repository'
+      end
+    end
+  end
+
   context 'creates branch if it does not exists' do
     let(:branch_name) { 'new_branch' }
     let(:opts) { file_opts.merge(branch_name: branch_name) }