Replace nested conditional with guard clauses (#8294)

Merge pull request 8294

.rubocop_todo.yml

@@ -14,5 +14,4 @@ Layout/SpaceAroundOperators:
   Exclude:
     - 'lib/jekyll/commands/build.rb'
     - 'lib/jekyll/site.rb'
-    - 'lib/jekyll/tags/include.rb'
     - 'test/test_configuration.rb'

lib/jekyll/tags/include.rb

@@ -253,20 +253,18 @@ module Jekyll
       end
 
       def page_path(context)
-        if context.registers[:page].nil?
-          context.registers[:site].source
-        else
-          site = context.registers[:site]
-          page_payload  = context.registers[:page]
-          resource_path = \
-            if page_payload["collection"].nil?
-              page_payload["path"]
-            else
-              File.join(site.config["collections_dir"], page_payload["path"])
-            end
-          resource_path.sub!(%r!/#excerpt\z!, "")
-          site.in_source_dir File.dirname(resource_path)
-        end
+        page, site = context.registers.values_at(:page, :site)
+        return site.source unless page
+
+        site.in_source_dir File.dirname(resource_path(page, site))
+      end
+
+      private
+
+      def resource_path(page, site)
+        path = page["path"]
+        path = File.join(site.config["collections_dir"], path) if page["collection"]
+        path.sub(%r!/#excerpt\z!, "")
       end
     end
   end