Improve parts of the example server config (#182)

Add a section for the new worker options and comment out some options
that have reasonable defaults or are uncommon to avoid confusion with
people thinking they are required or setting invalid values.

config/bulldozer.example.yml

@@ -19,10 +19,19 @@ logging:
   # Choose from: debug, info, warn, error
   level: debug
 
-# Options for the HTTP Cache
-cache:
-  # The maximum size of the cache (specified in human readable units)
-  max_size: 50 MB
+# Options for the GitHub response cache. When the cache reaches max_size, the
+# oldest entries are evicted. Size properties can use any format supported by
+# https://github.com/c2h5oh/datasize
+#
+# cache:
+#   max_size: "50MB"
+
+# Options for webhook processing workers. Events are dropped if the queue is
+# full. The defaults are shown below.
+#
+# workers:
+#   workers: 10
+#   queue_size: 100
 
 # Options for connecting to GitHub
 github:
@@ -52,19 +61,30 @@ github:
 options:
   # The path within repositories to find the bulldozer.yml config file
   configuration_path: .bulldozer.yml
+
   # The name of the application. This will affect the User-Agent header
   # when making requests to Github.
   app_name: bulldozer
-  # An optional personal access token associated with a normal GitHub user that
-  # is used to merge pull requests into protected branches with push
+
+  # Deprecated: An optional personal access token associated with a GitHub user
+  # that is used to merge pull requests into protected branches with push
   # restrictions. Can also be set by the BULLDOZER_PUSH_RESTRICTION_USER_TOKEN
   # environment variable.
-  push_restriction_user_token: token
-  # Default repository config, the same as the config file described in README
-  default_repository_config:
-    merge:
-      blacklist:
-        labels: ["do not merge"]
+  #
+  # This is not necessary on GitHub.com and GitHub Enterprise 2.20+, which
+  # allow applications in the push restriction list.
+  #
+  # push_restriction_user_token: token
+
+  # A default repository configuration to use if a repository does not define a
+  # configuration. The format is the same as the bulldozer.yml file. If unset
+  # (the default), Bulldozer ignores repositories that are missing a
+  # configuration file.
+  #
+  # default_repository_config:
+  #   merge:
+  #     blacklist:
+  #       labels: ["do not merge"]
 
 # Optional configuration to emit metrics to datadog
 datadog: