added the retries plugin, which hops on fetch_response and resends a request while it's retryable

lib/httpx/plugins/retries.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+module HTTPX
+  module Plugins
+    module Retries
+      MAX_RETRIES = 3
+
+      module InstanceMethods
+        def max_retries(n)
+          branch(default_options.with_max_retries(n.to_i))
+        end
+
+        private
+
+        def fetch_response(request)
+          response = super
+          if response.is_a?(ErrorResponse) &&
+              request.retries > 0
+            request.retries -= 1
+            channel = find_channel(request)
+            channel.send(request)
+            return
+          end
+          response
+        end
+      end
+
+      module RequestMethods
+        attr_accessor :retries
+        
+        def initialize(*args)
+          super
+          @retries = @options.max_retries || MAX_RETRIES
+        end
+      end
+
+      module OptionsMethods
+        def self.included(klass)
+          super
+          klass.def_option(:max_retries) do |num|
+            num = Integer(num)
+            raise Error, ":max_retries must be positive" unless num.positive?
+            num
+          end
+        end
+      end
+    end
+    register_plugin :retries, Retries 
+  end
+end