Remove CHANGED_PATH/URL CI variable code

This code was part of a proof-of-concept that lived behind a
feature flag that was never turned on. We don't need it, and
we should remove to code so as to prevent its use.

app/models/ci/build.rb

@@ -526,7 +526,6 @@ module Ci
           .concat(job_jwt_variables)
           .concat(scoped_variables)
           .concat(job_variables)
-          .concat(environment_changed_page_variables)
           .concat(persisted_environment_variables)
           .to_runner_variables
       end
@@ -563,15 +562,6 @@ module Ci
       end
     end
 
-    def environment_changed_page_variables
-      Gitlab::Ci::Variables::Collection.new.tap do |variables|
-        break variables unless environment_status && Feature.enabled?(:modifed_path_ci_variables, project)
-
-        variables.append(key: 'CI_MERGE_REQUEST_CHANGED_PAGE_PATHS', value: environment_status.changed_paths.join(','))
-        variables.append(key: 'CI_MERGE_REQUEST_CHANGED_PAGE_URLS', value: environment_status.changed_urls.join(','))
-      end
-    end
-
     def deploy_token_variables
       Gitlab::Ci::Variables::Collection.new.tap do |variables|
         break variables unless gitlab_deploy_token

app/models/environment_status.rb

@@ -72,14 +72,6 @@ class EnvironmentStatus
       .merge_request_diff_files.where(deleted_file: false)
   end
 
-  def changed_paths
-    changes.map { |change| change[:path] }
-  end
-
-  def changed_urls
-    changes.map { |change| change[:external_url] }
-  end
-
   def has_route_map?
     project.route_map_for(sha).present?
   end

config/feature_flags/development/modifed_path_ci_variables.yml

----
-name: modifed_path_ci_variables
-introduced_by_url: 
-rollout_issue_url: 
-group: 
-type: development
-default_enabled: false

spec/models/ci/build_spec.rb

@@ -2554,94 +2554,6 @@ RSpec.describe Ci::Build do
       end
     end
 
-    describe 'CHANGED_PAGES variables' do
-      let(:route_map_yaml) do
-        <<~ROUTEMAP
-        - source: 'bar/branch-test.txt'
-          public: '/bar/branches'
-        - source: 'with space/README.md'
-          public: '/README'
-        ROUTEMAP
-      end
-
-      before do
-        allow_any_instance_of(Project)
-          .to receive(:route_map_for).with(/.+/)
-          .and_return(Gitlab::RouteMap.new(route_map_yaml))
-      end
-
-      context 'with a deployment environment and a merge request' do
-        let(:merge_request) { create(:merge_request, source_project: project, target_project: project) }
-        let(:environment)   { create(:environment, project: merge_request.project, name: "foo-#{project.default_branch}") }
-        let(:build)         { create(:ci_build, pipeline: pipeline, environment: environment.name) }
-
-        let(:full_urls) do
-          [
-            File.join(environment.external_url, '/bar/branches'),
-            File.join(environment.external_url, '/README')
-          ]
-        end
-
-        it 'populates CI_MERGE_REQUEST_CHANGED_PAGES_* variables' do
-          expect(subject).to include(
-            {
-              key: 'CI_MERGE_REQUEST_CHANGED_PAGE_PATHS',
-              value: '/bar/branches,/README',
-              public: true,
-              masked: false
-            },
-            {
-              key: 'CI_MERGE_REQUEST_CHANGED_PAGE_URLS',
-              value: full_urls.join(','),
-              public: true,
-              masked: false
-            }
-          )
-        end
-
-        context 'with a deployment environment and no merge request' do
-          let(:environment)   { create(:environment, project: project, name: "foo-#{project.default_branch}") }
-          let(:build)         { create(:ci_build, pipeline: pipeline, environment: environment.name) }
-
-          it 'does not append CHANGED_PAGES variables' do
-            ci_variables = subject.select { |var| var[:key] =~ /MERGE_REQUEST_CHANGED_PAGES/ }
-
-            expect(ci_variables).to be_empty
-          end
-        end
-
-        context 'with no deployment environment and a present merge request' do
-          let(:merge_request) { create(:merge_request, :with_detached_merge_request_pipeline, source_project: project, target_project: project) }
-          let(:build)         { create(:ci_build, pipeline: merge_request.all_pipelines.take) }
-
-          it 'does not append CHANGED_PAGES variables' do
-            ci_variables = subject.select { |var| var[:key] =~ /MERGE_REQUEST_CHANGED_PAGES/ }
-
-            expect(ci_variables).to be_empty
-          end
-        end
-
-        context 'with no deployment environment and no merge request' do
-          it 'does not append CHANGED_PAGES variables' do
-            ci_variables = subject.select { |var| var[:key] =~ /MERGE_REQUEST_CHANGED_PAGES/ }
-
-            expect(ci_variables).to be_empty
-          end
-        end
-      end
-
-      context 'with the :modified_path_ci_variables feature flag disabled' do
-        before do
-          stub_feature_flags(modified_path_ci_variables: false)
-        end
-
-        it 'does not set CI_MERGE_REQUEST_CHANGED_PAGES_* variables' do
-          expect(subject.find { |var| var[:key] == 'CI_MERGE_REQUEST_CHANGED_PAGE_PATHS' }).to be_nil
-          expect(subject.find { |var| var[:key] == 'CI_MERGE_REQUEST_CHANGED_PAGE_URLS' }).to be_nil
-        end
-      end
-    end
-
     context 'when build has user' do
       let(:user_variables) do
         [

spec/models/environment_status_spec.rb

@@ -66,18 +66,6 @@ RSpec.describe EnvironmentStatus do
     end
   end
 
-  describe '#changed_paths' do
-    subject { environment_status.changed_urls }
-
-    it { is_expected.to contain_exactly("#{environment.external_url}/ruby-style-guide.html", "#{environment.external_url}/html/page.html") }
-  end
-
-  describe '#changed_urls' do
-    subject { environment_status.changed_paths }
-
-    it { is_expected.to contain_exactly('ruby-style-guide.html', 'html/page.html') }
-  end
-
   describe '.for_merge_request' do
     let(:admin) { create(:admin) }
     let!(:pipeline) { create(:ci_pipeline, sha: sha, merge_requests_as_head_pipeline: [merge_request]) }