Add arbitrary commit API backend changes

This commit moves some required entities from controller to API level, and implements a limit on the number of context commits that will be returned from the API.

app/controllers/projects/merge_requests/diffs_controller.rb

@@ -65,7 +65,7 @@ class Projects::MergeRequests::DiffsController < Projects::MergeRequests::Applic
     options = additional_attributes.merge(diff_view: diff_view)
 
     if @merge_request.project.context_commits_enabled?
-      options[:context_commits] = @merge_request.context_commits
+      options[:context_commits] = @merge_request.recent_context_commits
     end
 
     render json: DiffsSerializer.new(request).represent(diffs, options)

app/models/merge_request.rb

@@ -410,8 +410,16 @@ class MergeRequest < ApplicationRecord
     "#{project.to_reference_base(from, full: full)}#{reference}"
   end
 
-  def context_commits
-    @context_commits ||= merge_request_context_commits.map(&:to_commit)
+  def context_commits(limit: nil)
+    @context_commits ||= merge_request_context_commits.limit(limit).map(&:to_commit)
+  end
+
+  def recent_context_commits
+    context_commits(limit: MergeRequestDiff::COMMITS_SAFE_SIZE)
+  end
+
+  def context_commits_count
+    context_commits.count
   end
 
   def commits(limit: nil)

app/serializers/commit_entity.rb

 # frozen_string_literal: true
 
-class CommitEntity < API::Entities::Commit
-  include MarkupHelper
-  include RequestAwareEntity
-
-  expose :author, using: UserEntity
-
-  expose :author_gravatar_url do |commit|
-    GravatarService.new.execute(commit.author_email) # rubocop: disable CodeReuse/ServiceClass
-  end
-
-  expose :commit_url do |commit, options|
-    project_commit_url(request.project, commit, params: options.fetch(:commit_url_params, {}))
-  end
-
-  expose :commit_path do |commit, options|
-    project_commit_path(request.project, commit, params: options.fetch(:commit_url_params, {}))
-  end
-
-  expose :description_html, if: { type: :full } do |commit|
-    markdown_field(commit, :description)
-  end
-
-  expose :title_html, if: { type: :full } do |commit|
-    markdown_field(commit, :title)
-  end
-
-  expose :signature_html, if: { type: :full } do |commit|
-    render('projects/commit/_signature', signature: commit.signature) if commit.has_signature?
-  end
-
-  expose :pipeline_status_path, if: { type: :full } do |commit, options|
-    pipeline_ref = options[:pipeline_ref]
-    pipeline_project = options[:pipeline_project] || commit.project
-    next unless pipeline_ref && pipeline_project
-
-    pipeline = commit.latest_pipeline_for_project(pipeline_ref, pipeline_project)
-    next unless pipeline&.status
-
-    pipelines_project_commit_path(pipeline_project, commit.id, ref: pipeline_ref)
-  end
-
-  def render(*args)
-    return unless request.respond_to?(:render) && request.render.respond_to?(:call)
-
-    request.render.call(*args)
-  end
+class CommitEntity < API::Entities::CommitWithLink
 end

app/serializers/user_entity.rb

 # frozen_string_literal: true
 
-class UserEntity < API::Entities::UserBasic
-  include RequestAwareEntity
-  include UserStatusTooltip
-
-  expose :path do |user|
-    user_path(user)
-  end
+class UserEntity < API::Entities::UserPath
 end

lib/api/entities/commit_with_link.rb

+# frozen_string_literal: true
+
+module API
+  module Entities
+    class CommitWithLink < Commit
+      include MarkupHelper
+      include RequestAwareEntity
+
+      expose :author, using: Entities::UserPath
+
+      expose :author_gravatar_url do |commit|
+        GravatarService.new.execute(commit.author_email)
+      end
+
+      expose :commit_url do |commit, options|
+        project_commit_url(request.project, commit, params: options.fetch(:commit_url_params, {}))
+      end
+
+      expose :commit_path do |commit, options|
+        project_commit_path(request.project, commit, params: options.fetch(:commit_url_params, {}))
+      end
+
+      expose :description_html, if: { type: :full } do |commit|
+        markdown_field(commit, :description)
+      end
+
+      expose :title_html, if: { type: :full } do |commit|
+        markdown_field(commit, :title)
+      end
+
+      expose :signature_html, if: { type: :full } do |commit|
+        render('projects/commit/_signature', signature: commit.signature) if commit.has_signature?
+      end
+
+      expose :pipeline_status_path, if: { type: :full } do |commit, options|
+        pipeline_ref = options[:pipeline_ref]
+        pipeline_project = options[:pipeline_project] || commit.project
+        next unless pipeline_ref && pipeline_project
+
+        pipeline = commit.latest_pipeline_for_project(pipeline_ref, pipeline_project)
+        next unless pipeline&.status
+
+        pipelines_project_commit_path(pipeline_project, commit.id, ref: pipeline_ref)
+      end
+
+      def render(*args)
+        return unless request.respond_to?(:render) && request.render.respond_to?(:call)
+
+        request.render.call(*args)
+      end
+    end
+  end
+end

lib/api/entities/user_path.rb

+# frozen_string_literal: true
+
+module API
+  module Entities
+    class UserPath < UserBasic
+      include RequestAwareEntity
+      include UserStatusTooltip
+
+      expose :path do |user|
+        user_path(user)
+      end
+    end
+  end
+end

lib/api/merge_requests.rb

@@ -306,7 +306,7 @@ module API
         context_commits =
           paginate(merge_request.merge_request_context_commits).map(&:to_commit)
 
-        present context_commits, with: Entities::Commit
+        present context_commits, with: Entities::CommitWithLink, type: :full, request: merge_request
       end
 
       params do