Fix Cache#fetch instrumentation

Before this change, you couldn't tell if a read was a hit or not when
you called fetch.

activesupport/lib/active_support/cache.rb

@@ -277,13 +277,18 @@ def fetch(name, options = nil)
           options = merged_options(options)
           key = namespaced_key(name, options)
 
-          cached_entry = find_cached_entry(key, name, options) unless options[:force]
-          entry = handle_expired_entry(cached_entry, key, options)
+          instrument(:read, name, options) do |payload|
+            cached_entry = read_entry(key, options) unless options[:force]
+            payload[:super_operation] = :fetch if payload
+            entry = handle_expired_entry(cached_entry, key, options)
 
-          if entry
-            get_entry_value(entry, name, options)
-          else
-            save_block_result_to_cache(name, options) { |_name| yield _name }
+            if entry
+              payload[:hit] = true if payload
+              get_entry_value(entry, name, options)
+            else
+              payload[:hit] = false if payload
+              save_block_result_to_cache(name, options) { |_name| yield _name }
+            end
           end
         else
           read(name, options)
@@ -556,13 +561,6 @@ def log
           logger.debug(yield)
         end
 
-        def find_cached_entry(key, name, options)
-          instrument(:read, name, options) do |payload|
-            payload[:super_operation] = :fetch if payload
-            read_entry(key, options)
-          end
-        end
-
         def handle_expired_entry(entry, key, options)
           if entry && entry.expired?
             race_ttl = options[:race_condition_ttl].to_i