Add --prefix as a configure task parameter

lib/rscons/cli.rb

@@ -167,7 +167,7 @@ EOF
         if task.desc
           usage += %[  #{sprintf("%-27s", name)} #{task.desc}\n]
           task.params.each do |name, param|
-            usage += %[    #{sprintf("%-25s", "--#{name}")} #{param.description}]
+            usage += %[    #{sprintf("%-25s", "--#{param.cli_option}")} #{param.description}\n]
           end
         end
       end

lib/rscons/script.rb

@@ -41,12 +41,14 @@ module Rscons
       #
       # @param name [String]
       #   Param name.
-      # @param description [String]
-      #   Param description.
       # @param value [String, nil]
       #   Param value.
-      def param(name, description, value)
-        Task::Param.new(name, description, value)
+      # @param cli_option [String]
+      #   Param CLI option text.
+      # @param description [String]
+      #   Param description.
+      def param(name, value, cli_option, description)
+        Task::Param.new(name, value, cli_option, description)
       end
 
       # Return path components from the PATH variable.
@@ -306,7 +308,8 @@ module Rscons
         end
         task("configure",
              desc: "Configure the project",
-             autoconf: false) do
+             autoconf: false,
+             params: [param("prefix", "/usr/local", "prefix=PREFIX", "Set installation prefix (default: /usr/local)")]) do
           Rscons.application.configure
         end
         task("distclean",

lib/rscons/task.rb

@@ -56,6 +56,10 @@ module Rscons
       #   Param name.
       attr_reader :name
 
+      # @return [String]
+      #   Param CLI option text.
+      attr_reader :cli_option
+
       # @return [String]
       #   Param description.
       attr_reader :description
@@ -68,14 +72,17 @@ module Rscons
       #
       # @param name [String]
       #   Param name.
-      # @param description [String]
-      #   Param description.
       # @param value [String, nil]
       #   Param value.
-      def initialize(name, description, value)
+      # @param cli_option [String]
+      #   Param CLI option text.
+      # @param description [String]
+      #   Param description.
+      def initialize(name, value, cli_option, description)
         @name = name
-        @description = description
         @value = value
+        @cli_option = cli_option
+        @description = description
       end
 
     end