Improve & simplify GitHub's representation classes

lib/github/import.rb

@@ -211,7 +211,7 @@ module Github
         # for both features, like manipulating assignees, labels
         # and milestones, are provided within the Issues API.
         if representation.pull_request?
-          return unless representation.labels? || representation.has_comments?
+          return unless representation.labels? || representation.comments?
 
           merge_request = MergeRequest.find_by!(target_project_id: project.id, iid: representation.iid)
 
@@ -248,7 +248,7 @@ module Github
     end
 
     def fetch_comments_conditionally(issuable, representation)
-      if representation.has_comments?
+      if representation.comments?
         comments_url = "/repos/#{repo}/issues/#{issuable.iid}/comments"
         fetch_comments(issuable, :comment, comments_url)
       end

lib/github/representation/branch.rb

@@ -7,10 +7,14 @@ module Github
         raw.dig('user', 'login') || 'unknown'
       end
 
+      def repo?
+        raw['repo'].present?
+      end
+
       def repo
-        return @repo if defined?(@repo)
+        return unless repo?
 
-        @repo = Github::Representation::Repo.new(raw['repo']) if raw['repo'].present?
+        @repo ||= Github::Representation::Repo.new(raw['repo'])
       end
 
       def ref
@@ -25,12 +29,6 @@ module Github
         Commit.truncate_sha(sha)
       end
 
-      def exists?
-        return @exists if defined?(@exists)
-
-        @exists = repository.branch_exists?(ref)
-      end
-
       def valid?
         sha.present? && ref.present?
       end

lib/github/representation/issue.rb

@@ -5,7 +5,7 @@ module Github
         raw['state'] == 'closed' ? 'closed' : 'opened'
       end
 
-      def has_comments?
+      def comments?
         raw['comments'] > 0
       end
 

lib/github/representation/pull_request.rb

 module Github
   module Representation
     class PullRequest < Representation::Issuable
-      delegate :user, :repo, :ref, :sha, to: :source_branch, prefix: true
-      delegate :user, :exists?, :repo, :ref, :sha, :short_sha, to: :target_branch, prefix: true
+      delegate :sha, to: :source_branch, prefix: true
+      delegate :sha, to: :target_branch, prefix: true
 
       def source_project
         project
@@ -11,7 +11,7 @@ module Github
       def source_branch_name
         # Mimic the "user:branch" displayed in the MR widget,
         # i.e. "Request to merge rymai:add-external-mounts into master"
-        cross_project? ? "#{source_branch_user}:#{source_branch_ref}" : source_branch_ref
+        cross_project? ? "#{source_branch.user}:#{source_branch.ref}" : source_branch.ref
       end
 
       def target_project
@@ -19,7 +19,7 @@ module Github
       end
 
       def target_branch_name
-        target_branch_ref
+        target_branch.ref
       end
 
       def state
@@ -62,9 +62,9 @@ module Github
       end
 
       def cross_project?
-        return true if source_branch_repo.nil?
+        return true unless source_branch.repo?
 
-        source_branch_repo.id != target_branch_repo.id
+        source_branch.repo.id != target_branch.repo.id
       end
     end
   end