Add a semantic CLI option for no config file (#2689)

README.md

@@ -272,9 +272,13 @@ $ puma -C /path/to/config
 
 If no configuration file is specified, Puma will look for a configuration file at `config/puma.rb`. If an environment is specified, either via the `-e` and `--environment` flags, or through the `RACK_ENV` or the `RAILS_ENV` environment variables, Puma first looks for configuration at `config/puma/<environment_name>.rb`, and then falls back to `config/puma.rb`.
 
-If you want to prevent Puma from looking for a configuration file in those locations, provide a dash as the argument to the `-C` (or `--config`) flag:
+If you want to prevent Puma from looking for a configuration file in those locations, include the `--no-config` flag:
 
 ```
+$ puma -C --no-config
+
+# or
+
 $ puma -C "-"
 ```
 

lib/puma/cli.rb

@@ -112,6 +112,11 @@ def setup_options
             file_config.load arg
           end
 
+          # Identical to supplying --config "-", but more semantic
+          o.on "--no-config", "Prevent Puma from searching for a config file" do |arg|
+            file_config.load "-"
+          end
+
           o.on "--control-url URL", "The bind url to use for the control server. Use 'auto' to use temp unix server" do |arg|
             configure_control_url(arg)
           end