let config.file_watcher be the way to enable the evented file watcher

Before this commit, the sole presence of the Listen constant
enabled the evented file watcher (unless listen resorted to
the polling backend).

This way, applications may depend on listen for other stuff
independently of this feature. Also, allows teams with mixed
setups to decide at boot time whether the evented watcher
should be enabled for each particular instance.

1 files changed, 9 insertions, 4 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index d946fc1bbd..88558cde1c 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -7,13 +7,18 @@
     
     *Michael Grosser*
 
-*   Implements an evented file system monitor to asynchronously detect changes
-    in the application source code, routes, locales, etc.
+*   Implements an evented file watcher to asynchronously detect changes in the
+    application source code, routes, locales, etc.
 
-    To opt-in load the [listen](https://github.com/guard/listen) gem in `Gemfile`:
+    This watcher is disabled by default, applications my enable it in the configuration:
+
+        # config/environments/development.rb
+        config.file_watcher = ActiveSupport::EventedFileUpdateChecker
+
+    This feature depends on the [listen](https://github.com/guard/listen) gem:
 
         group :development do
-          gem 'listen', '~> 3.0.4'
+          gem 'listen', '~> 3.0.5'
         end
 
     *Puneet Agarwal* and *Xavier Noria*