Update the command line usage reference (#878)

src/en/ref/Command Line.adoc

@@ -2,39 +2,23 @@
 === Command Line Usage
 
 
-Grails incorporates the powerful build system http://gradle.org[Gradle].
+Grails incorporates a CLI and also uses the powerful build system https://gradle.org[Gradle].
 
 The basic usage scenario is:
 
-[source,groovy]
+[source,console]
 ----
-grails <<environment>>* <<command name>>
+grails <<command name>> <<options>>*
 ----
 
-Grails searches in the following directories for Gant scripts to execute:
+When running Gradle tasks you can specify the environment that the command executes in with an optional grails.env parameter, either with one of the built-in environment names:
 
-* `USER_HOME/.grails/scripts`
-* `PROJECT_HOME/src/main/scripts/`
-* `PROJECT_HOME/plugins/*/scripts`
-* `GRAILS_HOME/scripts`
-
-If multiple matches are found Grails will give you a choice of which one to execute.
-
-You can specify the environment that the command executes in with an optional grails.env parameter, either with one of the built-in environment names:
-
-[source,groovy]
+[source,console]
 ----
 ./gradlew bootRun -Dgrails.env=dev
 ./gradlew bootRun -Dgrails.env=test
 ./gradlew bootRun -Dgrails.env=prod
-
-----
-
-Or using a -D argument if the name is not one of the three standard names:
-
-[source,groovy]
-----
-grails -Dgrails.env=uat run-app
+./gradlew bootRun -Dgrails.env=custom
 ----
 
 Refer to the user guide section on link:{guidePath}/commandLine.html[The Command Line] for more information.