Add latest changes from gitlab-org/gitlab@13-2-stable-ee

19 files changed, 446 insertions, 82 deletions

diff --git a/app/controllers/concerns/controller_with_feature_category.rb b/app/controllers/concerns/controller_with_feature_category.rb
new file mode 100644
index 00000000000..f8985cf0950
--- /dev/null
+++ b/app/controllers/concerns/controller_with_feature_category.rb
@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+module ControllerWithFeatureCategory
+  extend ActiveSupport::Concern
+  include Gitlab::ClassAttributes
+
+  class_methods do
+    def feature_category(category, config = {})
+      validate_config!(config)
+
+      category_config = Config.new(category, config[:only], config[:except], config[:if], config[:unless])
+      # Add the config to the beginning. That way, the last defined one takes precedence.
+      feature_category_configuration.unshift(category_config)
+    end
+
+    def feature_category_for_action(action)
+      category_config = feature_category_configuration.find { |config| config.matches?(action) }
+
+      category_config&.category || superclass_feature_category_for_action(action)
+    end
+
+    private
+
+    def validate_config!(config)
+      invalid_keys = config.keys - [:only, :except, :if, :unless]
+      if invalid_keys.any?
+        raise ArgumentError, "unknown arguments: #{invalid_keys} "
+      end
+
+      if config.key?(:only) && config.key?(:except)
+        raise ArgumentError, "cannot configure both `only` and `except`"
+      end
+    end
+
+    def feature_category_configuration
+      class_attributes[:feature_category_config] ||= []
+    end
+
+    def superclass_feature_category_for_action(action)
+      return unless superclass.respond_to?(:feature_category_for_action)
+
+      superclass.feature_category_for_action(action)
+    end
+  end
+end
diff --git a/app/controllers/concerns/controller_with_feature_category/config.rb b/app/controllers/concerns/controller_with_feature_category/config.rb
new file mode 100644
index 00000000000..624691ee4f6
--- /dev/null
+++ b/app/controllers/concerns/controller_with_feature_category/config.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+module ControllerWithFeatureCategory
+  class Config
+    attr_reader :category
+
+    def initialize(category, only, except, if_proc, unless_proc)
+      @category = category.to_sym
+      @only, @except = only&.map(&:to_s), except&.map(&:to_s)
+      @if_proc, @unless_proc = if_proc, unless_proc
+    end
+
+    def matches?(action)
+      included?(action) && !excluded?(action) &&
+        if_proc?(action) && !unless_proc?(action)
+    end
+
+    private
+
+    attr_reader :only, :except, :if_proc, :unless_proc
+
+    def if_proc?(action)
+      if_proc.nil? || if_proc.call(action)
+    end
+
+    def unless_proc?(action)
+      unless_proc.present? && unless_proc.call(action)
+    end
+
+    def included?(action)
+      only.nil? || only.include?(action)
+    end
+
+    def excluded?(action)
+      except.present? && except.include?(action)
+    end
+  end
+end
diff --git a/app/controllers/concerns/filters_events.rb b/app/controllers/concerns/filters_events.rb
new file mode 100644
index 00000000000..c82d0318fd3
--- /dev/null
+++ b/app/controllers/concerns/filters_events.rb
@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+module FiltersEvents
+  def event_filter
+    @event_filter ||= new_event_filter.tap { |ef| cookies[:event_filter] = ef.filter }
+  end
+
+  private
+
+  def new_event_filter
+    active_filter = params[:event_filter].presence || cookies[:event_filter]
+    EventFilter.new(active_filter)
+  end
+end
diff --git a/app/controllers/concerns/integrations_actions.rb b/app/controllers/concerns/integrations_actions.rb
index cc9db7936e8..46febc44807 100644
--- a/app/controllers/concerns/integrations_actions.rb
+++ b/app/controllers/concerns/integrations_actions.rb
@@ -8,6 +8,9 @@ module IntegrationsActions
 
     before_action :not_found, unless: :integrations_enabled?
     before_action :integration, only: [:edit, :update, :test]
+    before_action only: :edit do
+      push_frontend_feature_flag(:integration_form_refactor, default_enabled: true)
+    end
   end
 
   def edit
@@ -51,9 +54,8 @@ module IntegrationsActions
   end
 
   def integration
-    # Using instance variable `@service` still required as it's used in ServiceParams
-    # and app/views/shared/_service_settings.html.haml. Should be removed once
-    # those 2 are refactored to use `@integration`.
+    # Using instance variable `@service` still required as it's used in ServiceParams.
+    # Should be removed once that is refactored to use `@integration`.
     @integration = @service ||= find_or_initialize_integration(params[:id]) # rubocop:disable Gitlab/ModuleWithInstanceVariables
   end
 
diff --git a/app/controllers/concerns/issuable_actions.rb b/app/controllers/concerns/issuable_actions.rb
index 98fa8202e25..c4dbce00593 100644
--- a/app/controllers/concerns/issuable_actions.rb
+++ b/app/controllers/concerns/issuable_actions.rb
@@ -110,9 +110,13 @@ module IssuableActions
 
   def bulk_update
     result = Issuable::BulkUpdateService.new(parent, current_user, bulk_update_params).execute(resource_name)
-    quantity = result[:count]
 
-    render json: { notice: "#{quantity} #{resource_name.pluralize(quantity)} updated" }
+    if result.success?
+      quantity = result.payload[:count]
+      render json: { notice: "#{quantity} #{resource_name.pluralize(quantity)} updated" }
+    elsif result.error?
+      render json: { errors: result.message }, status: result.http_status
+    end
   end
 
   # rubocop:disable CodeReuse/ActiveRecord
@@ -193,13 +197,13 @@ module IssuableActions
 
   def authorize_destroy_issuable!
     unless can?(current_user, :"destroy_#{issuable.to_ability_name}", issuable)
-      return access_denied!
+      access_denied!
     end
   end
 
   def authorize_admin_issuable!
     unless can?(current_user, :"admin_#{resource_name}", parent)
-      return access_denied!
+      access_denied!
     end
   end
 
diff --git a/app/controllers/concerns/issuable_collections.rb b/app/controllers/concerns/issuable_collections.rb
index 9ef067e8797..4f61e5ed711 100644
--- a/app/controllers/concerns/issuable_collections.rb
+++ b/app/controllers/concerns/issuable_collections.rb
@@ -81,34 +81,36 @@ module IssuableCollections
 
   # rubocop:disable Gitlab/ModuleWithInstanceVariables
   def finder_options
-    params[:state] = default_state if params[:state].blank?
-
-    options = {
-      scope: params[:scope],
-      state: params[:state],
-      confidential: Gitlab::Utils.to_boolean(params[:confidential]),
-      sort: set_sort_order
-    }
-
-    # Used by view to highlight active option
-    @sort = options[:sort]
-
-    # When a user looks for an exact iid, we do not filter by search but only by iid
-    if params[:search] =~ /^#(?<iid>\d+)\z/
-      options[:iids] = Regexp.last_match[:iid]
-      params[:search] = nil
+    strong_memoize(:finder_options) do
+      params[:state] = default_state if params[:state].blank?
+
+      options = {
+        scope: params[:scope],
+        state: params[:state],
+        confidential: Gitlab::Utils.to_boolean(params[:confidential]),
+        sort: set_sort_order
+      }
+
+      # Used by view to highlight active option
+      @sort = options[:sort]
+
+      # When a user looks for an exact iid, we do not filter by search but only by iid
+      if params[:search] =~ /^#(?<iid>\d+)\z/
+        options[:iids] = Regexp.last_match[:iid]
+        params[:search] = nil
+      end
+
+      if @project
+        options[:project_id] = @project.id
+        options[:attempt_project_search_optimizations] = true
+      elsif @group
+        options[:group_id] = @group.id
+        options[:include_subgroups] = true
+        options[:attempt_group_search_optimizations] = true
+      end
+
+      params.permit(finder_type.valid_params).merge(options)
     end
-
-    if @project
-      options[:project_id] = @project.id
-      options[:attempt_project_search_optimizations] = true
-    elsif @group
-      options[:group_id] = @group.id
-      options[:include_subgroups] = true
-      options[:attempt_group_search_optimizations] = true
-    end
-
-    params.permit(finder_type.valid_params).merge(options)
   end
   # rubocop:enable Gitlab/ModuleWithInstanceVariables
 
@@ -147,7 +149,10 @@ module IssuableCollections
                                 when 'Issue'
                                   common_attributes + [:project, project: :namespace]
                                 when 'MergeRequest'
-                                  common_attributes + [:target_project, :latest_merge_request_diff, source_project: :route, head_pipeline: :project, target_project: :namespace]
+                                  common_attributes + [
+                                    :target_project, :latest_merge_request_diff, :approvals, :approved_by_users,
+                                    source_project: :route, head_pipeline: :project, target_project: :namespace
+                                  ]
                                 end
   end
   # rubocop:enable Gitlab/ModuleWithInstanceVariables
diff --git a/app/controllers/concerns/known_sign_in.rb b/app/controllers/concerns/known_sign_in.rb
index c0b9605de58..cacc7e4628f 100644
--- a/app/controllers/concerns/known_sign_in.rb
+++ b/app/controllers/concerns/known_sign_in.rb
@@ -2,19 +2,34 @@
 
 module KnownSignIn
   include Gitlab::Utils::StrongMemoize
+  include CookiesHelper
+
+  KNOWN_SIGN_IN_COOKIE = :known_sign_in
+  KNOWN_SIGN_IN_COOKIE_EXPIRY = 14.days
 
   private
 
   def verify_known_sign_in
-    return unless current_user
+    return unless Gitlab::CurrentSettings.notify_on_unknown_sign_in? && current_user
+
+    notify_user unless known_device? || known_remote_ip?
 
-    notify_user unless known_remote_ip?
+    update_cookie
   end
 
   def known_remote_ip?
     known_ip_addresses.include?(request.remote_ip)
   end
 
+  def known_device?
+    cookies.encrypted[KNOWN_SIGN_IN_COOKIE] == current_user.id
+  end
+
+  def update_cookie
+    set_secure_cookie(KNOWN_SIGN_IN_COOKIE, current_user.id,
+                      type: COOKIE_TYPE_ENCRYPTED, httponly: true, expires: KNOWN_SIGN_IN_COOKIE_EXPIRY)
+  end
+
   def sessions
     strong_memoize(:session) do
       ActiveSession.list(current_user).reject(&:is_impersonated)
diff --git a/app/controllers/concerns/membership_actions.rb b/app/controllers/concerns/membership_actions.rb
index 4ab02005b45..8c7f156f7f8 100644
--- a/app/controllers/concerns/membership_actions.rb
+++ b/app/controllers/concerns/membership_actions.rb
@@ -31,7 +31,10 @@ module MembershipActions
 
   def destroy
     member = membershipable.members_and_requesters.find(params[:id])
-    Members::DestroyService.new(current_user).execute(member)
+    # !! is used in case unassign_issuables contains empty string which would result in nil
+    unassign_issuables = !!ActiveRecord::Type::Boolean.new.cast(params.delete(:unassign_issuables))
+
+    Members::DestroyService.new(current_user).execute(member, unassign_issuables: unassign_issuables)
 
     respond_to do |format|
       format.html do
diff --git a/app/controllers/concerns/metrics/dashboard/prometheus_api_proxy.rb b/app/controllers/concerns/metrics/dashboard/prometheus_api_proxy.rb
new file mode 100644
index 00000000000..e0e3f628cc5
--- /dev/null
+++ b/app/controllers/concerns/metrics/dashboard/prometheus_api_proxy.rb
@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+module Metrics::Dashboard::PrometheusApiProxy
+  extend ActiveSupport::Concern
+  include RenderServiceResults
+
+  included do
+    before_action :authorize_read_prometheus!, only: [:prometheus_proxy]
+  end
+
+  def prometheus_proxy
+    variable_substitution_result =
+      proxy_variable_substitution_service.new(proxyable, permit_params).execute
+
+    if variable_substitution_result[:status] == :error
+      return error_response(variable_substitution_result)
+    end
+
+    prometheus_result = Prometheus::ProxyService.new(
+      proxyable,
+      proxy_method,
+      proxy_path,
+      variable_substitution_result[:params]
+    ).execute
+
+    return continue_polling_response if prometheus_result.nil?
+    return error_response(prometheus_result) if prometheus_result[:status] == :error
+
+    success_response(prometheus_result)
+  end
+
+  private
+
+  def proxyable
+    raise NotImplementedError, "#{self.class} must implement method: #{__callee__}"
+  end
+
+  def proxy_variable_substitution_service
+    raise NotImplementedError, "#{self.class} must implement method: #{__callee__}"
+  end
+
+  def permit_params
+    params.permit!
+  end
+
+  def proxy_method
+    request.method
+  end
+
+  def proxy_path
+    params[:proxy_path]
+  end
+end
diff --git a/app/controllers/concerns/metrics_dashboard.rb b/app/controllers/concerns/metrics_dashboard.rb
index 1aea0e294a5..28d0692d748 100644
--- a/app/controllers/concerns/metrics_dashboard.rb
+++ b/app/controllers/concerns/metrics_dashboard.rb
@@ -13,7 +13,7 @@ module MetricsDashboard
     result = dashboard_finder.find(
       project_for_dashboard,
       current_user,
-      metrics_dashboard_params.to_h.symbolize_keys
+      decoded_params
     )
 
     if result
@@ -41,7 +41,7 @@ module MetricsDashboard
   end
 
   def amend_dashboard(dashboard)
-    project_dashboard = project_for_dashboard && !dashboard[:system_dashboard]
+    project_dashboard = project_for_dashboard && !dashboard[:out_of_the_box_dashboard]
 
     dashboard[:can_edit] = project_dashboard ? can_edit?(dashboard) : false
     dashboard[:project_blob_path] = project_dashboard ? dashboard_project_blob_path(dashboard) : nil
@@ -114,4 +114,14 @@ module MetricsDashboard
       json: result.slice(:all_dashboards, :message, :status)
     }
   end
+
+  def decoded_params
+    params = metrics_dashboard_params
+
+    if params[:dashboard_path]
+      params[:dashboard_path] = CGI.unescape(params[:dashboard_path])
+    end
+
+    params
+  end
 end
diff --git a/app/controllers/concerns/notes_actions.rb b/app/controllers/concerns/notes_actions.rb
index d3dfb1813e4..f4fc7decb60 100644
--- a/app/controllers/concerns/notes_actions.rb
+++ b/app/controllers/concerns/notes_actions.rb
@@ -5,6 +5,11 @@ module NotesActions
   include Gitlab::Utils::StrongMemoize
   extend ActiveSupport::Concern
 
+  # last_fetched_at is an integer number of microseconds, which is the same
+  # precision as PostgreSQL "timestamp" fields. It's important for them to have
+  # identical precision for accurate pagination
+  MICROSECOND = 1_000_000
+
   included do
     before_action :set_polling_interval_header, only: [:index]
     before_action :require_noteable!, only: [:index, :create]
@@ -13,30 +18,20 @@ module NotesActions
   end
 
   def index
-    notes_json = { notes: [], last_fetched_at: Time.current.to_i }
-
-    notes = notes_finder
-              .execute
-              .inc_relations_for_view
-
-    if notes_filter != UserPreference::NOTES_FILTERS[:only_comments]
-      notes =
-        ResourceEvents::MergeIntoNotesService
-          .new(noteable, current_user, last_fetched_at: last_fetched_at)
-          .execute(notes)
-    end
-
+    notes, meta = gather_notes
     notes = prepare_notes_for_rendering(notes)
     notes = notes.select { |n| n.readable_by?(current_user) }
-
-    notes_json[:notes] =
+    notes =
       if use_note_serializer?
         note_serializer.represent(notes)
       else
         notes.map { |note| note_json(note) }
       end
 
-    render json: notes_json
+    # We know there's more data, so tell the frontend to poll again after 1ms
+    set_polling_interval_header(interval: 1) if meta[:more]
+
+    render json: meta.merge(notes: notes)
   end
 
   # rubocop:disable Gitlab/ModuleWithInstanceVariables
@@ -101,6 +96,48 @@ module NotesActions
 
   private
 
+  # Lower bound (last_fetched_at as specified in the request) is already set in
+  # the finder. Here, we select between returning all notes since then, or a
+  # page's worth of notes.
+  def gather_notes
+    if Feature.enabled?(:paginated_notes, project)
+      gather_some_notes
+    else
+      gather_all_notes
+    end
+  end
+
+  def gather_all_notes
+    now = Time.current
+    notes = merge_resource_events(notes_finder.execute.inc_relations_for_view)
+
+    [notes, { last_fetched_at: (now.to_i * MICROSECOND) + now.usec }]
+  end
+
+  def gather_some_notes
+    paginator = Gitlab::UpdatedNotesPaginator.new(
+      notes_finder.execute.inc_relations_for_view,
+      last_fetched_at: last_fetched_at
+    )
+
+    notes = paginator.notes
+
+    # Fetch all the synthetic notes in the same time range as the real notes.
+    # Although we don't limit the number, their text is under our control so
+    # should be fairly cheap to process.
+    notes = merge_resource_events(notes, fetch_until: paginator.next_fetched_at)
+
+    [notes, paginator.metadata]
+  end
+
+  def merge_resource_events(notes, fetch_until: nil)
+    return notes if notes_filter == UserPreference::NOTES_FILTERS[:only_comments]
+
+    ResourceEvents::MergeIntoNotesService
+      .new(noteable, current_user, last_fetched_at: last_fetched_at, fetch_until: fetch_until)
+      .execute(notes)
+  end
+
   def note_html(note)
     render_to_string(
       "shared/notes/_note",
@@ -226,11 +263,11 @@ module NotesActions
   end
 
   def update_note_params
-    params.require(:note).permit(:note)
+    params.require(:note).permit(:note, :position)
   end
 
-  def set_polling_interval_header
-    Gitlab::PollingInterval.set_header(response, interval: 6_000)
+  def set_polling_interval_header(interval: 6000)
+    Gitlab::PollingInterval.set_header(response, interval: interval)
   end
 
   def noteable
@@ -242,7 +279,14 @@ module NotesActions
   end
 
   def last_fetched_at
-    request.headers['X-Last-Fetched-At']
+    strong_memoize(:last_fetched_at) do
+      microseconds = request.headers['X-Last-Fetched-At'].to_i
+
+      seconds = microseconds / MICROSECOND
+      frac = microseconds % MICROSECOND
+
+      Time.zone.at(seconds, frac)
+    end
   end
 
   def notes_filter
diff --git a/app/controllers/concerns/renders_member_access.rb b/app/controllers/concerns/renders_member_access.rb
index 955ac1a1bc8..745830181c1 100644
--- a/app/controllers/concerns/renders_member_access.rb
+++ b/app/controllers/concerns/renders_member_access.rb
@@ -7,12 +7,6 @@ module RendersMemberAccess
     groups
   end
 
-  def prepare_projects_for_rendering(projects)
-    preload_max_member_access_for_collection(Project, projects)
-
-    projects
-  end
-
   private
 
   # rubocop: disable CodeReuse/ActiveRecord
diff --git a/app/controllers/concerns/renders_projects_list.rb b/app/controllers/concerns/renders_projects_list.rb
new file mode 100644
index 00000000000..be45c676ad6
--- /dev/null
+++ b/app/controllers/concerns/renders_projects_list.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module RendersProjectsList
+  def prepare_projects_for_rendering(projects)
+    preload_max_member_access_for_collection(Project, projects)
+
+    # Call the forks count method on every project, so the BatchLoader would load them all at
+    # once when the entities are rendered
+    projects.each(&:forks_count)
+
+    projects
+  end
+end
diff --git a/app/controllers/concerns/service_params.rb b/app/controllers/concerns/service_params.rb
index e78fa8f8250..a19c43a227a 100644
--- a/app/controllers/concerns/service_params.rb
+++ b/app/controllers/concerns/service_params.rb
@@ -22,8 +22,8 @@ module ServiceParams
     :comment_on_event_enabled,
     :comment_detail,
     :confidential_issues_events,
+    :confluence_url,
     :default_irc_uri,
-    :description,
     :device,
     :disable_diffs,
     :drone_url,
@@ -31,6 +31,7 @@ module ServiceParams
     :external_wiki_url,
     :google_iap_service_account_json,
     :google_iap_audience_client_id,
+    :inherit_from_id,
     # We're using `issues_events` and `merge_requests_events`
     # in the view so we still need to explicitly state them
     # here. `Service#event_names` would only give
@@ -61,7 +62,6 @@ module ServiceParams
     :sound,
     :subdomain,
     :teamcity_url,
-    :title,
     :token,
     :type,
     :url,
diff --git a/app/controllers/concerns/snippets/blobs_actions.rb b/app/controllers/concerns/snippets/blobs_actions.rb
new file mode 100644
index 00000000000..db56ce8f193
--- /dev/null
+++ b/app/controllers/concerns/snippets/blobs_actions.rb
@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+module Snippets::BlobsActions
+  extend ActiveSupport::Concern
+
+  include Gitlab::Utils::StrongMemoize
+  include ExtractsRef
+  include Snippets::SendBlob
+
+  included do
+    before_action :authorize_read_snippet!, only: [:raw]
+    before_action :ensure_repository
+    before_action :ensure_blob
+  end
+
+  def raw
+    send_snippet_blob(snippet, blob)
+  end
+
+  private
+
+  def repository_container
+    snippet
+  end
+
+  # rubocop:disable Gitlab/ModuleWithInstanceVariables
+  def blob
+    strong_memoize(:blob) do
+      assign_ref_vars
+
+      next unless @commit
+
+      @repo.blob_at(@commit.id, @path)
+    end
+  end
+  # rubocop:enable Gitlab/ModuleWithInstanceVariables
+
+  def ensure_blob
+    render_404 unless blob
+  end
+
+  def ensure_repository
+    unless snippet.repo_exists?
+      Gitlab::AppLogger.error(message: "Snippet raw blob attempt with no repo", snippet: snippet.id)
+
+      respond_422
+    end
+  end
+
+  def snippet_id
+    params[:snippet_id]
+  end
+end
diff --git a/app/controllers/concerns/snippets/send_blob.rb b/app/controllers/concerns/snippets/send_blob.rb
new file mode 100644
index 00000000000..4f432430aaa
--- /dev/null
+++ b/app/controllers/concerns/snippets/send_blob.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+module Snippets::SendBlob
+  include SendsBlob
+
+  def send_snippet_blob(snippet, blob)
+    workhorse_set_content_type!
+
+    send_blob(
+      snippet.repository,
+      blob,
+      inline: content_disposition == 'inline',
+      allow_caching: snippet.public?
+    )
+  end
+
+  private
+
+  def content_disposition
+    @disposition ||= params[:inline] == 'false' ? 'attachment' : 'inline'
+  end
+end
diff --git a/app/controllers/concerns/snippets_actions.rb b/app/controllers/concerns/snippets_actions.rb
index 51fc12398d9..048b18c5c61 100644
--- a/app/controllers/concerns/snippets_actions.rb
+++ b/app/controllers/concerns/snippets_actions.rb
@@ -2,11 +2,13 @@
 
 module SnippetsActions
   extend ActiveSupport::Concern
-  include SendsBlob
+
   include RendersNotes
   include RendersBlob
   include PaginatedCollection
   include Gitlab::NoteableMetadata
+  include Snippets::SendBlob
+  include SnippetsSort
 
   included do
     skip_before_action :verify_authenticity_token,
@@ -25,6 +27,10 @@ module SnippetsActions
     render 'edit'
   end
 
+  # This endpoint is being replaced by Snippets::BlobController#raw
+  # Support for old raw links will be maintainted via this action but
+  # it will only return the first blob found,
+  # see: https://gitlab.com/gitlab-org/gitlab/-/issues/217775
   def raw
     workhorse_set_content_type!
 
@@ -39,12 +45,7 @@ module SnippetsActions
         filename: Snippet.sanitized_file_name(blob.name)
       )
     else
-      send_blob(
-        snippet.repository,
-        blob,
-        inline: content_disposition == 'inline',
-        allow_caching: snippet.public?
-      )
+      send_snippet_blob(snippet, blob)
     end
   end
 
@@ -106,10 +107,6 @@ module SnippetsActions
 
   private
 
-  def content_disposition
-    @disposition ||= params[:inline] == 'false' ? 'attachment' : 'inline'
-  end
-
   # rubocop:disable Gitlab/ModuleWithInstanceVariables
   def blob
     return unless snippet
diff --git a/app/controllers/concerns/snippets_sort.rb b/app/controllers/concerns/snippets_sort.rb
new file mode 100644
index 00000000000..f122c843af7
--- /dev/null
+++ b/app/controllers/concerns/snippets_sort.rb
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+module SnippetsSort
+  extend ActiveSupport::Concern
+
+  def sort_param
+    params[:sort].presence || 'updated_desc'
+  end
+end
diff --git a/app/controllers/concerns/wiki_actions.rb b/app/controllers/concerns/wiki_actions.rb
index 7eef12fadfe..a5182000f5b 100644
--- a/app/controllers/concerns/wiki_actions.rb
+++ b/app/controllers/concerns/wiki_actions.rb
@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 module WikiActions
+  include DiffHelper
+  include PreviewMarkdown
   include SendsBlob
   include Gitlab::Utils::StrongMemoize
   extend ActiveSupport::Concern
@@ -11,16 +13,23 @@ module WikiActions
     before_action :authorize_admin_wiki!, only: :destroy
 
     before_action :wiki
-    before_action :page, only: [:show, :edit, :update, :history, :destroy]
+    before_action :page, only: [:show, :edit, :update, :history, :destroy, :diff]
     before_action :load_sidebar, except: [:pages]
+    before_action :set_content_class
 
     before_action only: [:show, :edit, :update] do
       @valid_encoding = valid_encoding?
     end
 
     before_action only: [:edit, :update], unless: :valid_encoding? do
-      redirect_to wiki_page_path(wiki, page)
+      if params[:id].present?
+        redirect_to wiki_page_path(wiki, page || params[:id])
+      else
+        redirect_to wiki_path(wiki)
+      end
     end
+
+    helper_method :view_file_button, :diff_file_html_data
   end
 
   def new
@@ -133,6 +142,19 @@ module WikiActions
   # rubocop:enable Gitlab/ModuleWithInstanceVariables
 
   # rubocop:disable Gitlab/ModuleWithInstanceVariables
+  def diff
+    return render_404 unless page
+
+    apply_diff_view_cookie!
+
+    @diffs = page.diffs(diff_options)
+    @diff_notes_disabled = true
+
+    render 'shared/wikis/diff'
+  end
+  # rubocop:disable Gitlab/ModuleWithInstanceVariables
+
+  # rubocop:disable Gitlab/ModuleWithInstanceVariables
   def destroy
     WikiPages::DestroyService.new(container: container, current_user: current_user).execute(page)
 
@@ -203,7 +225,7 @@ module WikiActions
 
   def page_params
     keys = [:id]
-    keys << :version_id if params[:action] == 'show'
+    keys << :version_id if %w[show diff].include?(params[:action])
 
     params.values_at(*keys)
   end
@@ -229,4 +251,25 @@ module WikiActions
       wiki.repository.blob_at(commit.id, params[:id])
     end
   end
+
+  def set_content_class
+    @content_class = 'limit-container-width' unless fluid_layout # rubocop:disable Gitlab/ModuleWithInstanceVariables
+  end
+
+  # Override CommitsHelper#view_file_button
+  def view_file_button(commit_sha, *args)
+    path = wiki_page_path(wiki, page, version_id: page.version.id)
+
+    helpers.link_to(path, class: 'btn') do
+      helpers.raw(_('View page @ ')) + helpers.content_tag(:span, Commit.truncate_sha(commit_sha), class: 'commit-sha')
+    end
+  end
+
+  # Override DiffHelper#diff_file_html_data
+  def diff_file_html_data(_project, _diff_file_path, diff_commit_id)
+    {
+      blob_diff_path: wiki_page_path(wiki, page, action: :diff, version_id: diff_commit_id),
+      view: diff_view
+    }
+  end
 end