Retrieve PR comments only when we know there are any

The Pull Request resource doesn't include the `comments` field, while
the Issue resource does. And since we're looping through all issues
anyway, we can freely check if the issue is a PR and has comments and in
this case only fetch comments for it.

That means if you have 1000 PRs but only 200 with comments, you will do
200 API requests instead of 1000. :notbad:
Signed-off-by: Rémy Coutable <remy@rymai.me>

lib/github/client.rb

 module Github
   class Client
     TIMEOUT = 60
+    DEFAULT_PER_PAGE = 100
 
     attr_reader :connection, :rate_limit
 
@@ -20,7 +21,7 @@ module Github
       exceed, reset_in = rate_limit.get
       sleep reset_in if exceed
 
-      Github::Response.new(connection.get(url, query))
+      Github::Response.new(connection.get(url, { per_page: DEFAULT_PER_PAGE }.merge(query)))
     end
 
     private

lib/github/import.rb

@@ -115,7 +115,7 @@ module Github
       url = "/repos/#{repo}/labels"
 
       while url
-        response = Github::Client.new(options).get(url, per_page: 100)
+        response = Github::Client.new(options).get(url)
 
         response.body.each do |raw|
           begin
@@ -139,7 +139,7 @@ module Github
       url = "/repos/#{repo}/milestones"
 
       while url
-        response = Github::Client.new(options).get(url, state: :all, per_page: 100)
+        response = Github::Client.new(options).get(url, state: :all)
 
         response.body.each do |raw|
           begin
@@ -168,7 +168,7 @@ module Github
       url = "/repos/#{repo}/pulls"
 
       while url
-        response = Github::Client.new(options).get(url, state: :all, sort: :created, direction: :asc, per_page: 100)
+        response = Github::Client.new(options).get(url, state: :all, sort: :created, direction: :asc)
 
         response.body.each do |raw|
           pull_request  = Github::Representation::PullRequest.new(raw, options.merge(project: project))
@@ -202,13 +202,8 @@ module Github
             merge_request.save!(validate: false)
             merge_request.merge_request_diffs.create
 
-            # Fetch review comments
             review_comments_url = "/repos/#{repo}/pulls/#{pull_request.iid}/comments"
             fetch_comments(merge_request, :review_comment, review_comments_url, LegacyDiffNote)
-
-            # Fetch comments
-            comments_url = "/repos/#{repo}/issues/#{pull_request.iid}/comments"
-            fetch_comments(merge_request, :comment, comments_url)
           rescue => e
             error(:pull_request, pull_request.url, e.message)
           ensure
@@ -224,7 +219,7 @@ module Github
       url = "/repos/#{repo}/issues"
 
       while url
-        response = Github::Client.new(options).get(url, state: :all, sort: :created, direction: :asc, per_page: 100)
+        response = Github::Client.new(options).get(url, state: :all, sort: :created, direction: :asc)
 
         response.body.each { |raw| populate_issue(raw) }
 
@@ -241,12 +236,17 @@ module Github
         # for both features, like manipulating assignees, labels
         # and milestones, are provided within the Issues API.
         if representation.pull_request?
-          return unless representation.has_labels?
+          return if !representation.has_labels? && !representation.has_comments?
 
           merge_request = MergeRequest.find_by!(target_project_id: project.id, iid: representation.iid)
+
+          if representation.has_labels?
             merge_request.update_attribute(:label_ids, label_ids(representation.labels))
+          end
+
+          fetch_comments_conditionally(merge_request, representation)
         else
-          return if Issue.where(iid: representation.iid, project_id: project.id).exists?
+          return if Issue.exists?(iid: representation.iid, project_id: project.id)
 
           author_id          = user_id(representation.author, project.creator_id)
           issue              = Issue.new
@@ -263,20 +263,23 @@ module Github
           issue.updated_at   = representation.updated_at
           issue.save!(validate: false)
 
-          # Fetch comments
-          if representation.has_comments?
-            comments_url = "/repos/#{repo}/issues/#{issue.iid}/comments"
-            fetch_comments(issue, :comment, comments_url)
-          end
+          fetch_comments_conditionally(issue, representation)
         end
       rescue => e
         error(:issue, representation.url, e.message)
       end
     end
 
+    def fetch_comments_conditionally(issuable, representation)
+      if representation.has_comments?
+        comments_url = "/repos/#{repo}/issues/#{issuable.iid}/comments"
+        fetch_comments(issuable, :comment, comments_url)
+      end
+    end
+
     def fetch_comments(noteable, type, url, klass = Note)
       while url
-        comments = Github::Client.new(options).get(url, per_page: 100)
+        comments = Github::Client.new(options).get(url)
 
         ActiveRecord::Base.no_touching do
           comments.body.each do |raw|
@@ -308,7 +311,7 @@ module Github
       url = "/repos/#{repo}/releases"
 
       while url
-        response = Github::Client.new(options).get(url, per_page: 100)
+        response = Github::Client.new(options).get(url)
 
         response.body.each do |raw|
           representation = Github::Representation::Release.new(raw)