Pass snippet branch to ls_files calls

Also add a `Snippet.default_branch` helper with a fallback to the
currently hardcoded 'master'.

app/models/snippet.rb

@@ -214,7 +214,7 @@ class Snippet < ApplicationRecord
   def blobs
     return [] unless repository_exists?
 
-    repository.ls_files(repository.root_ref).map { |file| Blob.lazy(repository, repository.root_ref, file) }
+    repository.ls_files(default_branch).map { |file| Blob.lazy(repository, default_branch, file) }
   end
 
   def hook_attrs
@@ -309,6 +309,11 @@ class Snippet < ApplicationRecord
     end
   end
 
+  override :default_branch
+  def default_branch
+    super || 'master'
+  end
+
   def repository_storage
     snippet_repository&.shard_name || self.class.pick_repository_storage
   end
@@ -336,17 +341,17 @@ class Snippet < ApplicationRecord
   def file_name_on_repo
     return if repository.empty?
 
-    list_files(repository.root_ref).first
+    list_files(default_branch).first
   end
 
   def list_files(ref = nil)
     return [] if repository.empty?
 
-    repository.ls_files(ref)
+    repository.ls_files(ref || default_branch)
   end
 
   def multiple_files?
-    list_files(repository.root_ref).size > 1
+    list_files.size > 1
   end
 
   class << self

app/models/snippet_repository.rb

@@ -93,7 +93,7 @@ class SnippetRepository < ApplicationRecord
   end
 
   def get_last_empty_file_index
-    repository.ls_files(nil).inject(0) do |max, file|
+    repository.ls_files(snippet.default_branch).inject(0) do |max, file|
       idx = file[EMPTY_FILE_PATTERN, 1].to_i
       [idx, max].max
     end

app/models/snippet_statistics.rb

@@ -25,7 +25,7 @@ class SnippetStatistics < ApplicationRecord
 
   def update_file_count
     count = if snippet.repository_exists?
-              repository.ls_files(repository.root_ref).size
+              repository.ls_files(snippet.default_branch).size
             else
               0
             end

app/services/snippets/create_service.rb

@@ -82,7 +82,7 @@ module Snippets
 
     def create_commit
       commit_attrs = {
-        branch_name: 'master',
+        branch_name: @snippet.default_branch,
         message: 'Initial commit'
       }
 

app/services/snippets/repository_validation_service.rb

@@ -39,7 +39,7 @@ module Snippets
     def check_branch_name_default!
       branches = repository.branch_names
 
-      return if branches.first == Gitlab::Checks::SnippetCheck::DEFAULT_BRANCH
+      return if branches.first == snippet.default_branch
 
       raise RepositoryValidationError, _('Repository has an invalid default branch name.')
     end
@@ -51,7 +51,7 @@ module Snippets
     end
 
     def check_file_count!
-      file_count = repository.ls_files(nil).size
+      file_count = repository.ls_files(snippet.default_branch).size
       limit = Snippet.max_file_limit(current_user)
 
       if file_count > limit

app/services/snippets/update_service.rb

@@ -93,7 +93,7 @@ module Snippets
       raise UpdateError unless snippet.snippet_repository
 
       commit_attrs = {
-        branch_name: 'master',
+        branch_name: snippet.default_branch,
         message: 'Update snippet'
       }
 

lib/gitlab/checks/snippet_check.rb

@@ -3,7 +3,6 @@
 module Gitlab
   module Checks
     class SnippetCheck < BaseChecker
-      DEFAULT_BRANCH = 'master'.freeze
       ERROR_MESSAGES = {
         create_delete_branch: 'You can not create or delete branches.'
       }.freeze
@@ -11,17 +10,18 @@ module Gitlab
       ATTRIBUTES = %i[oldrev newrev ref branch_name tag_name logger].freeze
       attr_reader(*ATTRIBUTES)
 
-      def initialize(change, logger:)
+      def initialize(change, default_branch:, logger:)
         @oldrev, @newrev, @ref = change.values_at(:oldrev, :newrev, :ref)
         @branch_name = Gitlab::Git.branch_name(@ref)
         @tag_name = Gitlab::Git.tag_name(@ref)
 
+        @default_branch = default_branch
         @logger = logger
         @logger.append_message("Running checks for ref: #{@branch_name || @tag_name}")
       end
 
       def validate!
-        if creation? || deletion?
+        if !@default_branch || creation? || deletion?
           raise GitAccess::ForbiddenError, ERROR_MESSAGES[:create_delete_branch]
         end
 
@@ -31,7 +31,7 @@ module Gitlab
       private
 
       def creation?
-        @branch_name != DEFAULT_BRANCH && super
+        @branch_name != @default_branch && super
       end
     end
   end

lib/gitlab/git_access_snippet.rb

@@ -119,7 +119,7 @@ module Gitlab
 
     override :check_single_change_access
     def check_single_change_access(change, _skip_lfs_integrity_check: false)
-      Checks::SnippetCheck.new(change, logger: logger).validate!
+      Checks::SnippetCheck.new(change, default_branch: snippet.default_branch, logger: logger).validate!
       Checks::PushFileCountCheck.new(change, repository: repository, limit: Snippet.max_file_limit(user), logger: logger).validate!
     rescue Checks::TimedLogger::TimeoutError
       raise TimeoutError, logger.full_message

spec/lib/gitlab/background_migration/backfill_snippet_repositories_spec.rb

@@ -327,6 +327,6 @@ RSpec.describe Gitlab::BackgroundMigration::BackfillSnippetRepositories, :migrat
   end
 
   def ls_files(snippet)
-    raw_repository(snippet).ls_files(nil)
+    raw_repository(snippet).ls_files(snippet.default_branch)
   end
 end

spec/lib/gitlab/checks/snippet_check_spec.rb

@@ -5,10 +5,12 @@ require 'spec_helper'
 RSpec.describe Gitlab::Checks::SnippetCheck do
   include_context 'change access checks context'
 
-  let(:snippet) { create(:personal_snippet, :repository) }
+  let_it_be(:snippet) { create(:personal_snippet, :repository) }
+
   let(:user_access) { Gitlab::UserAccessSnippet.new(user, snippet: snippet) }
+  let(:default_branch) { snippet.default_branch }
 
-  subject { Gitlab::Checks::SnippetCheck.new(changes, logger: logger) }
+  subject { Gitlab::Checks::SnippetCheck.new(changes, default_branch: default_branch, logger: logger) }
 
   describe '#validate!' do
     it 'does not raise any error' do
@@ -39,5 +41,13 @@ RSpec.describe Gitlab::Checks::SnippetCheck do
         end
       end
     end
+
+    context 'when default_branch is nil' do
+      let(:default_branch) { nil }
+
+      it 'raises an error' do
+        expect { subject.validate! }.to raise_error(Gitlab::GitAccess::ForbiddenError, 'You can not create or delete branches.')
+      end
+    end
   end
 end

spec/models/snippet_repository_spec.rb

@@ -108,6 +108,7 @@ RSpec.describe SnippetRepository do
       before do
         allow(snippet).to receive(:repository).and_return(repo)
         allow(repo).to receive(:ls_files).and_return([])
+        allow(repo).to receive(:root_ref).and_return('master')
       end
 
       it 'infers the commit action based on the parameters if not present' do
@@ -197,7 +198,7 @@ RSpec.describe SnippetRepository do
 
     shared_examples 'snippet repository with file names' do |*filenames|
       it 'sets a name for unnamed files' do
-        ls_files = snippet.repository.ls_files(nil)
+        ls_files = snippet.repository.ls_files(snippet.default_branch)
         expect(ls_files).to include(*filenames)
       end
     end
@@ -306,6 +307,6 @@ RSpec.describe SnippetRepository do
   end
 
   def first_blob(snippet)
-    snippet.repository.blob_at('master', snippet.repository.ls_files(nil).first)
+    snippet.repository.blob_at('master', snippet.repository.ls_files(snippet.default_branch).first)
   end
 end

spec/models/snippet_spec.rb

@@ -744,6 +744,16 @@ RSpec.describe Snippet do
 
         subject
       end
+
+      context 'when ref is nil' do
+        let(:ref) { nil }
+
+        it 'lists files from the repository from the deafult_branch' do
+          expect(snippet.repository).to receive(:ls_files).with(snippet.default_branch)
+
+          subject
+        end
+      end
     end
 
     context 'when snippet does not have a repository' do

spec/models/snippet_statistics_spec.rb

@@ -36,7 +36,7 @@ RSpec.describe SnippetStatistics do
     subject { statistics.update_file_count }
 
     it 'updates the count of files' do
-      file_count = snippet_with_repo.repository.ls_files(nil).count
+      file_count = snippet_with_repo.repository.ls_files(snippet_with_repo.default_branch).count
 
       subject