diff --git a/config/feature_flags/development/mirror_only_branches_match_regex.yml b/config/feature_flags/development/mirror_only_branches_match_regex.yml
new file mode 100644
index 0000000000000000000000000000000000000000..6494569b364d014a0b7a62510e731bc2f3fa5e50
--- /dev/null
+++ b/config/feature_flags/development/mirror_only_branches_match_regex.yml
@@ -0,0 +1,8 @@
+---
+name: mirror_only_branches_match_regex
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/99201
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/381667
+milestone: '15.6'
+type: development
+group: "group::source code"
+default_enabled: false
diff --git a/ee/app/controllers/ee/projects/mirrors_controller.rb b/ee/app/controllers/ee/projects/mirrors_controller.rb
index e885a218c8bff6260d56a78daf6d0de8ebb8561e..5ff52a97d6463c772a6fe9165009283c18094799 100644
--- a/ee/app/controllers/ee/projects/mirrors_controller.rb
+++ b/ee/app/controllers/ee/projects/mirrors_controller.rb
@@ -50,7 +50,9 @@ def update_now
 
       def mirror_params_attributes
         if can?(current_user, :admin_mirror, project)
-          super + mirror_params_attributes_ee
+          attributes = super
+          attributes[0][:remote_mirrors_attributes].push(:mirror_branch_regex) if mirror_branch_regex_enabled?
+          attributes + mirror_params_attributes_ee
         else
           super
         end
@@ -89,8 +91,32 @@ def safe_mirror_params
           end
         end
 
+        # avoid enable only_protected_branches and mirror_branch_regex at the same time
+        remote_mirror_data = params[:remote_mirrors_attributes]
+        if remote_mirror_data.present?
+          remote_mirror_data.transform_values! do |value|
+            format_remote_mirrors_attributes(value)
+            value
+          end
+        end
+
         params
       end
+
+      # Pass mirror_branch_regex and only_protected_branches at same time will use mirror_branch_regex
+      def format_remote_mirrors_attributes(params)
+        return unless params.is_a?(ActionController::Parameters)
+
+        if mirror_branch_regex_enabled? && params[:mirror_branch_regex].present?
+          params[:only_protected_branches] = false
+        end
+
+        params[:mirror_branch_regex] = nil if params[:only_protected_branches].present?
+      end
+
+      def mirror_branch_regex_enabled?
+        ::Feature.enabled?(:mirror_only_branches_match_regex, project)
+      end
     end
   end
 end
diff --git a/ee/app/models/concerns/mirror_configuration.rb b/ee/app/models/concerns/mirror_configuration.rb
new file mode 100644
index 0000000000000000000000000000000000000000..c3c719c283b5d246feb44fe22aa79dccb9442949
--- /dev/null
+++ b/ee/app/models/concerns/mirror_configuration.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+module MirrorConfiguration
+  MIRROR_BRANCHES_SETTING = {
+    all: 'all',
+    protected: 'protected',
+    regex: 'regex'
+  }.freeze
+
+  def mirror_branches_setting
+    return MIRROR_BRANCHES_SETTING[:protected] if only_mirror_protected_branches_column
+    return MIRROR_BRANCHES_SETTING[:regex] if mirror_branch_regex.present?
+
+    MIRROR_BRANCHES_SETTING[:all]
+  end
+
+  def only_mirror_protected_branches_column
+    raise NotImplementedError
+  end
+end
diff --git a/ee/app/models/ee/project.rb b/ee/app/models/ee/project.rb
index d27062774927861a054a90e202b9970aa745699e..6e62b2354ade5556d9cf23fd6d31f19348266e2a 100644
--- a/ee/app/models/ee/project.rb
+++ b/ee/app/models/ee/project.rb
@@ -34,6 +34,7 @@ def inapplicable_to_branch(branch)
       include UsageStatistics
       include ProjectSecurityScannersInformation
       include VulnerabilityFlagHelpers
+      include MirrorConfiguration
 
       before_update :update_legacy_open_source_license_available, if: -> { visibility_level_changed? }
 
@@ -232,6 +233,7 @@ def lock_for_confirmation!(id)
                :only_allow_merge_if_all_status_checks_passed,
                :only_allow_merge_if_all_status_checks_passed=,
                to: :project_setting
+      delegate :mirror_branch_regex, :mirror_branch_regex=, to: :project_setting
 
       validates :repository_size_limit,
         numericality: { only_integer: true, greater_than_or_equal_to: 0, allow_nil: true }
@@ -972,6 +974,10 @@ def any_external_status_checks_not_passed?(merge_request)
       status_checks.any? { |check| check.status(merge_request, merge_request.diff_head_sha) != 'passed' }
     end
 
+    def only_mirror_protected_branches_column
+      only_mirror_protected_branches
+    end
+
     private
 
     def update_legacy_open_source_license_available
diff --git a/ee/app/models/ee/project_setting.rb b/ee/app/models/ee/project_setting.rb
index 759068c24db98bca241cf3c78324ad5236a52ace..bf0df6e65f41c5eedc697b44db74e3837c455596 100644
--- a/ee/app/models/ee/project_setting.rb
+++ b/ee/app/models/ee/project_setting.rb
@@ -8,6 +8,9 @@ module ProjectSetting
       belongs_to :push_rule
 
       scope :has_vulnerabilities, -> { where('has_vulnerabilities IS TRUE') }
+
+      validates :mirror_branch_regex, absence: true, if: -> { project&.only_mirror_protected_branches? }
+      validates :mirror_branch_regex, untrusted_regexp: true, length: { maximum: 255 }
     end
 
     def selective_code_owner_removals
diff --git a/ee/app/models/ee/remote_mirror.rb b/ee/app/models/ee/remote_mirror.rb
index afa6e3155d2a3ef0d74dbfe980d22232cfbec500..c001fb2b83dcd75cad4ccfe6d0c2b946d2d4d5dd 100644
--- a/ee/app/models/ee/remote_mirror.rb
+++ b/ee/app/models/ee/remote_mirror.rb
@@ -4,8 +4,36 @@ module EE
   module RemoteMirror
     extend ActiveSupport::Concern
 
+    prepended do
+      include MirrorConfiguration
+
+      validates :mirror_branch_regex, absence: true, if: -> { only_protected_branches? }
+      validates :mirror_branch_regex, untrusted_regexp: true, length: { maximum: 255 }
+    end
+
     def sync?
       super && !::Gitlab::Geo.secondary?
     end
+
+    def only_mirror_protected_branches_column
+      only_protected_branches
+    end
+
+    def options_for_update
+      return super unless ::Feature.enabled?(:mirror_only_branches_match_regex, project)
+
+      options = super
+      options[:only_branches_matching] = branches_to_sync if mirror_branch_regex.present?
+
+      options
+    end
+
+    def branches_to_sync
+      branch_filter = ::Gitlab::UntrustedRegexp.new(mirror_branch_regex)
+
+      project.repository.branch_names.select do |branch_name|
+        branch_filter.match?(branch_name)
+      end
+    end
   end
 end
diff --git a/ee/app/services/ee/projects/update_service.rb b/ee/app/services/ee/projects/update_service.rb
index 4025dd142149d2e11e0c898e40185234e6d9060e..1347a0eb5cb19a63e1f8d3364d5f4e0058f633bb 100644
--- a/ee/app/services/ee/projects/update_service.rb
+++ b/ee/app/services/ee/projects/update_service.rb
@@ -14,6 +14,7 @@ module UpdateService
         only_mirror_protected_branches
         mirror_overwrites_diverged_branches
         import_data_attributes
+        mirror_branch_regex
       ].freeze
 
       override :execute
@@ -23,6 +24,7 @@ def execute
 
         shared_runners_setting
         mirror_user_setting
+        mirror_branch_setting
         compliance_framework_setting
 
         return update_failed! if project.errors.any?
@@ -113,6 +115,20 @@ def mirror_user_setting
         end
       end
 
+      def mirror_branch_setting
+        if mirror_branch_regex_enabled? && params[:mirror_branch_regex].present?
+          params[:only_mirror_protected_branches] = false
+        end
+
+        params.delete(:mirror_branch_regex) unless mirror_branch_regex_enabled?
+
+        params[:mirror_branch_regex] = nil if params[:only_mirror_protected_branches]
+      end
+
+      def mirror_branch_regex_enabled?
+        ::Feature.enabled?(:mirror_only_branches_match_regex, project)
+      end
+
       def compliance_framework_setting
         settings = params[:compliance_framework_setting_attributes]
         return unless settings.present?
diff --git a/ee/app/services/projects/update_mirror_service.rb b/ee/app/services/projects/update_mirror_service.rb
index 12b7435db45b151088c61818d4a354e4cf6c8ed5..a453851f71e30113172283264989d27e9108f6ab 100644
--- a/ee/app/services/projects/update_mirror_service.rb
+++ b/ee/app/services/projects/update_mirror_service.rb
@@ -193,10 +193,28 @@ def repository_tags_with_target
       repository.tags.select(&:dereferenced_target)
     end
 
-    def skip_branch?(name)
+    def skip_mismatched_branch?(name)
+      mirror_branch_regex_enabled? &&
+        project.mirror_branch_regex.present? &&
+        !branch_regex.match?(name)
+    end
+
+    def mirror_branch_regex_enabled?
+      ::Feature.enabled?(:mirror_only_branches_match_regex, project)
+    end
+
+    def branch_regex
+      @branch_regex ||= Gitlab::UntrustedRegexp.new(project.mirror_branch_regex)
+    end
+
+    def skip_unprotected_branch?(name)
       project.only_mirror_protected_branches && !ProtectedBranch.protected?(project, name)
     end
 
+    def skip_branch?(name)
+      skip_unprotected_branch?(name) || skip_mismatched_branch?(name)
+    end
+
     def service_logger
       @service_logger ||= Gitlab::UpdateMirrorServiceJsonLogger.build
     end
diff --git a/ee/spec/controllers/projects/mirrors_controller_spec.rb b/ee/spec/controllers/projects/mirrors_controller_spec.rb
index 90314b2ed06404e4fb3e67de7d1fd14d58ffbeda..3cab6330c9dc2b8269b6935b44d9751977d13c04 100644
--- a/ee/spec/controllers/projects/mirrors_controller_spec.rb
+++ b/ee/spec/controllers/projects/mirrors_controller_spec.rb
@@ -24,6 +24,42 @@
           do_put(project, remote_mirrors_attributes: { '0' => { 'enabled' => 1, 'url' => url } })
         end.to change { RemoteMirror.count }.to(1)
       end
+
+      it 'allows to create a remote mirror with mirror_branch_regex' do
+        expect do
+          do_put(project, remote_mirrors_attributes: { '0' => { enabled: 1, url: url, mirror_branch_regex: 'test' } })
+        end.to change { RemoteMirror.where(mirror_branch_regex: 'test').count }.to(1)
+      end
+
+      it 'allows only mirror protected branches' do
+        expect do
+          do_put(project, remote_mirrors_attributes: { '0' => { enabled: 1, url: url, only_protected_branches: true } })
+        end.to change { RemoteMirror.where(only_protected_branches: true, mirror_branch_regex: nil).count }.to(1)
+      end
+
+      it 'allows mirror all branches' do
+        expect do
+          do_put(project, remote_mirrors_attributes: { '0' => { enabled: 1, url: url } })
+        end.to change { RemoteMirror.where(only_protected_branches: false, mirror_branch_regex: nil).count }.to(1)
+      end
+
+      it 'do not allow invalid regex' do
+        do_put(project, remote_mirrors_attributes: { '0' => { enabled: 1, url: url, mirror_branch_regex: '\\' } } )
+        expect(response).to redirect_to(project_settings_repository_path(project, anchor: 'js-push-remote-settings'))
+        expect(flash[:alert]).to match(/Remote mirrors mirror branch regex not valid RE2 syntax: trailing/)
+      end
+
+      context 'when `mirror_only_branches_match_regex` FF is disabled' do
+        before do
+          stub_feature_flags(mirror_only_branches_match_regex: false)
+        end
+
+        it 'ignores mirror_branch_regex parameter' do
+          expect do
+            do_put(project, remote_mirrors_attributes: { '0' => { enabled: 1, url: url, mirror_branch_regex: 'test' } })
+          end.not_to change { RemoteMirror.where(mirror_branch_regex: 'test').count }
+        end
+      end
     end
 
     context 'when the current project has a remote mirror' do
@@ -225,6 +261,49 @@
         expect(flash[:alert]).to match(/is blocked/)
       end
     end
+
+    context 'setting up project mirror branches setting' do
+      it 'mirror all branches' do
+        do_put(project, only_mirror_protected_branches: false, mirror_branch_regex: nil)
+        project.reload
+        expect(project.only_mirror_protected_branches).to be_falsey
+        expect(project.mirror_branch_regex).to be_nil
+      end
+
+      it 'enable mirror_branch_regex would ignore only_mirror_protected_branches' do
+        do_put(project, only_mirror_protected_branches: true, mirror_branch_regex: 'text')
+        project.reload
+        expect(project.only_mirror_protected_branches).to be_falsey
+        expect(project.mirror_branch_regex).to eq('text')
+      end
+
+      it 'enable mirror_branch_regex would disable only_protected_branches' do
+        project.update!(only_mirror_protected_branches: true)
+        do_put(project, mirror_branch_regex: 'text')
+        project.reload
+        expect(project.only_mirror_protected_branches).to be_falsey
+        expect(project.mirror_branch_regex).to eq 'text'
+      end
+
+      it 'do not allow invalid regex' do
+        do_put(project, mirror_branch_regex: '\\')
+        expect(response).to redirect_to(project_settings_repository_path(project, anchor: 'js-push-remote-settings'))
+        expect(flash[:alert]).to match(/Project setting mirror branch regex not valid RE2 syntax: trailing/)
+      end
+
+      context 'when `mirror_only_branches_match_regex` FF is disabled' do
+        before do
+          stub_feature_flags(mirror_only_branches_match_regex: false)
+        end
+
+        it 'ignores mirror_branch_regex parameter' do
+          do_put(project, { mirror_branch_regex: 'test' } )
+          project.reload
+          expect(project.only_mirror_protected_branches).to be_falsey
+          expect(project.mirror_branch_regex).to be_nil
+        end
+      end
+    end
   end
 
   def do_put(project, options, extra_attrs = {})
diff --git a/ee/spec/models/concerns/mirror_configuration_spec.rb b/ee/spec/models/concerns/mirror_configuration_spec.rb
new file mode 100644
index 0000000000000000000000000000000000000000..1c4c00ffdfed9462d8ecad212803437df798df9c
--- /dev/null
+++ b/ee/spec/models/concerns/mirror_configuration_spec.rb
@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe MirrorConfiguration do
+  let(:klazz) { Class.new { include MirrorConfiguration } }
+
+  subject(:instance) { klazz.new }
+
+  describe '#only_mirror_protected_branches_column?' do
+    it 'raises NotImplementedError' do
+      expect { subject.only_mirror_protected_branches_column }.to raise_error(NotImplementedError)
+    end
+  end
+end
diff --git a/ee/spec/models/ee/project_setting_spec.rb b/ee/spec/models/ee/project_setting_spec.rb
index 323413377c6f6615e40493dad4cb169c689c1371..4acf0fd5396184a96d90a7e52c3f703d8a2390dc 100644
--- a/ee/spec/models/ee/project_setting_spec.rb
+++ b/ee/spec/models/ee/project_setting_spec.rb
@@ -13,4 +13,31 @@
 
     it { is_expected.to contain_exactly(setting_1) }
   end
+
+  describe 'validations' do
+    context 'when enable only_mirror_protected_branches and mirror_branch_regex' do
+      it 'is invalid' do
+        project = build(:project, only_mirror_protected_branches: true )
+        setting = build(:project_setting, project: project, mirror_branch_regex: 'text')
+
+        expect(setting).not_to be_valid
+      end
+    end
+
+    context 'when disable only_mirror_protected_branches and enable mirror_branch_regex' do
+      let_it_be(:project) { build(:project, only_mirror_protected_branches: false) }
+
+      it 'is valid' do
+        setting = build(:project_setting, project: project, mirror_branch_regex: 'test')
+
+        expect(setting).to be_valid
+      end
+
+      it 'is invalid with invalid regex' do
+        setting = build(:project_setting, project: project, mirror_branch_regex: '\\')
+
+        expect(setting).not_to be_valid
+      end
+    end
+  end
 end
diff --git a/ee/spec/models/project_spec.rb b/ee/spec/models/project_spec.rb
index 72cecf1227b7b5f28c7398b8f29f4717ef0a9b58..c936cae74c76ed8f7fb0faa871cd357c7a3e7951 100644
--- a/ee/spec/models/project_spec.rb
+++ b/ee/spec/models/project_spec.rb
@@ -3670,4 +3670,24 @@ def stub_default_url_options(host)
       expect(result).to be_empty
     end
   end
+
+  describe '#mirror_branches_setting' do
+    it 'mirror all branches' do
+      project = build(:project, only_mirror_protected_branches: false, mirror_branch_regex: nil)
+
+      expect(project.mirror_branches_setting).to eq('all')
+    end
+
+    it 'mirror protected branches' do
+      project = build(:project, only_mirror_protected_branches: true, mirror_branch_regex: nil)
+
+      expect(project.mirror_branches_setting).to eq('protected')
+    end
+
+    it 'mirror branches match regex' do
+      project = build(:project, only_mirror_protected_branches: false, mirror_branch_regex: 'text')
+
+      expect(project.mirror_branches_setting).to eq('regex')
+    end
+  end
 end
diff --git a/ee/spec/models/remote_mirror_spec.rb b/ee/spec/models/remote_mirror_spec.rb
index c842b385f8504dd67896c67d7d5a7df44a1686f9..22945152a62aa3763e3e97c76eecf7301b0fb0c9 100644
--- a/ee/spec/models/remote_mirror_spec.rb
+++ b/ee/spec/models/remote_mirror_spec.rb
@@ -5,6 +5,30 @@
 RSpec.describe RemoteMirror do
   let(:project) { create(:project, :repository, :remote_mirror) }
 
+  describe 'validations' do
+    context 'when enable only_protected_branches and mirror_branch_regex' do
+      it 'is invalid' do
+        remote_mirror = build(:remote_mirror, only_protected_branches: true, mirror_branch_regex: 'text')
+
+        expect(remote_mirror).not_to be_valid
+      end
+    end
+
+    context 'when disable only_protected_branches and enable mirror_branch_regex' do
+      it 'is valid' do
+        remote_mirror = build(:remote_mirror, only_protected_branches: false, mirror_branch_regex: 'test')
+
+        expect(remote_mirror).to be_valid
+      end
+
+      it 'is invalid with invalid regex' do
+        remote_mirror = build(:remote_mirror, only_protected_branches: false, mirror_branch_regex: '\\')
+
+        expect(remote_mirror).not_to be_valid
+      end
+    end
+  end
+
   describe '#sync' do
     let(:remote_mirror) { project.remote_mirrors.first }
 
@@ -16,4 +40,50 @@
       end
     end
   end
+
+  describe '#only_mirror_protected_branches_column' do
+    it 'returns true as only_protected_branches enabled' do
+      remote_mirror = build_stubbed(:remote_mirror, only_protected_branches: true)
+
+      expect(remote_mirror.only_mirror_protected_branches_column).to be_truthy
+    end
+
+    it 'returns false as only_protected_branches return' do
+      remote_mirror = build_stubbed(:remote_mirror, only_protected_branches: false)
+
+      expect(remote_mirror.only_mirror_protected_branches_column).to be_falsy
+    end
+  end
+
+  describe '#options_for_update' do
+    context 'when mirror_branch_regex is set' do
+      let(:user) { build(:user) }
+      let(:mirror) do
+        build(:remote_mirror,
+              project: project,
+              only_protected_branches: false,
+              mirror_branch_regex: '^matched*')
+      end
+
+      before do
+        project.repository.create_branch('matched', create_commit)
+        project.repository.create_branch('mismatched', create_commit)
+      end
+
+      it 'only sync matched and recently updated branch' do
+        options = mirror.options_for_update
+
+        expect(options).to include(only_branches_matching: %w[matched])
+      end
+    end
+  end
+
+  def create_commit
+    project.repository.commit_files(
+      user,
+      branch_name: 'HEAD',
+      message: 'commit message',
+      actions: []
+    )
+  end
 end
diff --git a/ee/spec/services/projects/update_mirror_service_spec.rb b/ee/spec/services/projects/update_mirror_service_spec.rb
index d767bb2a32be9f035163bf2de45b2da8740c5009..5a71a229681437ecd8096badd5ee0f6ad300bc41 100644
--- a/ee/spec/services/projects/update_mirror_service_spec.rb
+++ b/ee/spec/services/projects/update_mirror_service_spec.rb
@@ -327,6 +327,47 @@
           end
         end
 
+        context 'when mirror_branch_regex is set' do
+          let(:new_branch_name) { "new-branch" }
+          let(:existing_branch_name) { "existing-branch" }
+          let(:fake_regex) { instance_spy(Gitlab::UntrustedRegexp) }
+          let!(:project_setting) { create(:project_setting, project: project, mirror_branch_regex: 'fake_regex') }
+
+          before do
+            allow(Gitlab::UntrustedRegexp).to receive(:new)
+                                    .with('fake_regex')
+                                    .and_return(fake_regex)
+
+            allow(fake_regex).to receive(:match?).and_return(false)
+          end
+
+          it 'create a new matched branch' do
+            allow(fake_regex).to receive(:match?).with(new_branch_name).and_return(true)
+            service.execute
+            expect(project.repository.branch_names).to include(new_branch_name)
+          end
+
+          it 'does not create mismatched branch' do
+            service.execute
+            expect(project.repository.branch_names).not_to include(new_branch_name)
+          end
+
+          it 'updates existing matched branches' do
+            allow(fake_regex).to receive(:match?).with('existing-branch').and_return(true)
+            service.execute
+
+            expect(project.repository.find_branch(existing_branch_name).dereferenced_target)
+              .to eq(project.repository.find_branch(master).dereferenced_target)
+          end
+
+          it 'does not update mismatched branches' do
+            service.execute
+
+            expect(project.repository.find_branch(existing_branch_name).dereferenced_target)
+              .not_to eq(project.repository.find_branch(master).dereferenced_target)
+          end
+        end
+
         context 'with diverged branches' do
           let(:diverged_branch) { "markdown" }
 
diff --git a/ee/spec/services/projects/update_service_spec.rb b/ee/spec/services/projects/update_service_spec.rb
index b920f72bcc2d9a4f768aeb7a5ee057437f100849..61bf47ba63a03a11a613a75563155fedbbc265f1 100644
--- a/ee/spec/services/projects/update_service_spec.rb
+++ b/ee/spec/services/projects/update_service_spec.rb
@@ -120,6 +120,48 @@
 
       update_project(project, user, opts)
     end
+
+    context 'when update mirror branch setting' do
+      before do
+        project.team.add_maintainer(admin)
+      end
+
+      it 'allow mirror_branch_regex to be updated' do
+        result = update_project(project, admin, opts.merge(mirror_branch_regex: :test))
+
+        expect(result).to eq(status: :success)
+        expect(project.mirror_branch_regex).to match('test')
+      end
+
+      it 'enable only_mirror_protected_branches would clean mirror_branch_regex' do
+        project.mirror_branch_regex = 'test'
+        result = update_project(project, admin, opts.merge(only_mirror_protected_branches: true))
+
+        expect(result).to eq(status: :success)
+        expect(project.mirror_branch_regex).to be_nil
+      end
+
+      it 'fill mirror_branch_regex would disable only_mirror_protected_branches' do
+        project.only_mirror_protected_branches = true
+        result = update_project(project, admin, opts.merge(mirror_branch_regex: 'text'))
+
+        expect(result).to eq(status: :success)
+        expect(project.only_mirror_protected_branches).to be_falsey
+      end
+
+      context 'when `mirror_only_branches_match_regex` FF is disabled' do
+        before do
+          stub_feature_flags(mirror_only_branches_match_regex: false)
+        end
+
+        it 'ignores mirror_branch_regex parameter' do
+          result = update_project(project, admin, opts.merge(mirror_branch_regex: 'text'))
+
+          expect(result).to eq(status: :success)
+          expect(project.mirror_branch_regex).to be_nil
+        end
+      end
+    end
   end
 
   context 'audit events' do
diff --git a/spec/requests/api/project_attributes.yml b/spec/requests/api/project_attributes.yml
index 2ff4cd72f1ea4e963645b6b094eef44457cf1b80..da478a3547e605c63608b3c7feb4b967e154d8c6 100644
--- a/spec/requests/api/project_attributes.yml
+++ b/spec/requests/api/project_attributes.yml
@@ -43,6 +43,7 @@ itself: # project
     - storage_version
     - topic_list
     - updated_at
+    - mirror_branch_regex
   remapped_attributes:
     avatar: avatar_url
     build_allow_git_fetch: build_git_strategy