Add signatureHtml field for last-commit GQL

It allows FE to display signature for the last commit

app/assets/javascripts/repository/components/last_commit.vue

@@ -125,6 +125,7 @@ export default {
           </pre>
         </div>
         <div class="commit-actions flex-row">
+          <div v-if="commit.signatureHtml" v-html="commit.signatureHtml"></div>
           <gl-link
             v-if="commit.latestPipeline"
             v-gl-tooltip

app/assets/javascripts/repository/queries/pathLastCommit.query.graphql

@@ -13,6 +13,7 @@ query pathLastCommit($projectPath: ID!, $path: String, $ref: String!) {
             avatarUrl
             webUrl
           }
+          signatureHtml
           latestPipeline {
             detailedStatus {
               detailsPath

app/graphql/resolvers/last_commit_resolver.rb

+# frozen_string_literal: true
+
+module Resolvers
+  class LastCommitResolver < BaseResolver
+    type Types::CommitType, null: true
+
+    alias_method :tree, :object
+
+    def resolve(**args)
+      # Ensure merge commits can be returned by sending nil to Gitaly instead of '/'
+      path = tree.path == '/' ? nil : tree.path
+      commit = Gitlab::Git::Commit.last_for_path(tree.repository, tree.sha, path)
+
+      ::Commit.new(commit, tree.repository.project) if commit
+    end
+  end
+end

app/graphql/types/commit_type.rb

@@ -15,6 +15,8 @@ module Types
     field :message, type: GraphQL::STRING_TYPE, null: true # rubocop:disable Graphql/Descriptions
     field :authored_date, type: Types::TimeType, null: true # rubocop:disable Graphql/Descriptions
     field :web_url, type: GraphQL::STRING_TYPE, null: false # rubocop:disable Graphql/Descriptions
+    field :signature_html, type: GraphQL::STRING_TYPE,
+      null: true, calls_gitaly: true, description: 'Rendered html for the commit signature'
 
     # models/commit lazy loads the author by email
     field :author, type: Types::UserType, null: true # rubocop:disable Graphql/Descriptions

app/graphql/types/tree/tree_type.rb

@@ -7,9 +7,9 @@ module Types
       graphql_name 'Tree'
 
       # Complexity 10 as it triggers a Gitaly call on each render
-      field :last_commit, Types::CommitType, null: true, complexity: 10, calls_gitaly: true, resolve: -> (tree, args, ctx) do # rubocop:disable Graphql/Descriptions
-        tree.repository.last_commit_for_path(tree.sha, tree.path)
-      end
+      field :last_commit, Types::CommitType,
+        null: true, complexity: 10, calls_gitaly: true, resolver: Resolvers::LastCommitResolver,
+        description: 'Last commit for the tree'
 
       field :trees, Types::Tree::TreeEntryType.connection_type, null: false, resolve: -> (obj, args, ctx) do # rubocop:disable Graphql/Descriptions
         Gitlab::Graphql::Representation::TreeEntry.decorate(obj.trees, obj.repository)

app/presenters/commit_presenter.rb

@@ -20,4 +20,15 @@ class CommitPresenter < Gitlab::View::Presenter::Delegated
   def web_url
     Gitlab::UrlBuilder.new(commit).url
   end
+
+  def signature_html
+    return unless commit.has_signature?
+
+    ApplicationController.renderer.render(
+      'projects/commit/_signature',
+      locals: { signature: commit.signature },
+      layout: false,
+      formats: [:html]
+    )
+  end
 end

spec/graphql/resolvers/last_commit_resolver_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Resolvers::LastCommitResolver do
+  include GraphqlHelpers
+
+  let(:repository) { create(:project, :repository).repository }
+  let(:tree) { repository.tree(ref, path) }
+
+  let(:commit) { resolve(described_class, obj: tree) }
+
+  describe '#resolve' do
+    context 'last commit is a merge commit' do
+      let(:ref) { 'master' }
+      let(:path) { '/' }
+
+      it 'resolves to the merge commit' do
+        expect(commit).to eq(repository.commits(ref, limit: 1).last)
+      end
+    end
+
+    context 'last commit for a different branch and path' do
+      let(:ref) { 'fix' }
+      let(:path) { 'files' }
+
+      it 'resolves commit' do
+        expect(commit).to eq(repository.commits(ref, path: path, limit: 1).last)
+      end
+    end
+
+    context 'last commit does not exist' do
+      let(:ref) { 'master' }
+      let(:path) { 'does-not-exist' }
+
+      it 'returns nil' do
+        expect(commit).to be_nil
+      end
+    end
+  end
+end

spec/graphql/types/commit_type_spec.rb

@@ -7,5 +7,10 @@ describe GitlabSchema.types['Commit'] do
 
   it { expect(described_class).to require_graphql_authorizations(:download_code) }
 
-  it { expect(described_class).to have_graphql_fields(:id, :sha, :title, :description, :message, :authored_date, :author, :web_url, :latest_pipeline) }
+  it 'contains attributes related to commit' do
+    expect(described_class).to have_graphql_fields(
+      :id, :sha, :title, :description, :message, :authored_date,
+      :author, :web_url, :latest_pipeline, :signature_html
+    )
+  end
 end

spec/presenters/commit_presenter_spec.rb

@@ -55,4 +55,17 @@ describe CommitPresenter do
       end
     end
   end
+
+  describe '#signature_html' do
+    let(:signature) { 'signature' }
+
+    before do
+      expect(commit).to receive(:has_signature?).and_return(true)
+      allow(ApplicationController.renderer).to receive(:render).and_return(signature)
+    end
+
+    it 'renders html for displaying signature' do
+      expect(presenter.signature_html).to eq(signature)
+    end
+  end
 end