Add a command line option to print out the value of a particular configuration value.

features/command_line.feature

@@ -247,6 +247,23 @@ Feature: Command Line
       | sass_dir | sass       |
       | css_dir  | assets/css |
 
+  @now
+  Scenario Outline: Print out a configuration value
+    Given I am using the existing project in test/fixtures/stylesheets/compass
+    When I run: compass config -p <property>
+    Then I should see the following output: <value>
+    And the command exits <exit>
+  
+    Examples:
+      | property        | value                    | exit     |
+      | extensions_dir  | extensions               | normally |
+      | extensions_path | $PROJECT_PATH/extensions | normally |
+      | css_dir         | tmp                      | normally |
+      | css_path        | $PROJECT_PATH/tmp        | normally |
+      | sass_dir        | sass                     | normally |
+      | sass_path       | $PROJECT_PATH/sass       | normally |
+      | foobar          | ERROR: configuration property 'foobar' does not exist | with a non-zero error code |
+
   Scenario: Validate the generated CSS
     Given I am using the existing project in test/fixtures/stylesheets/compass
     When I run: compass validate

features/step_definitions/command_line_steps.rb

@@ -155,6 +155,9 @@ Then /^the command exits with a non\-zero error code$/ do
   @last_exit_code.should_not == 0
 end
 
+Then /^the command exits normally$/ do
+  @last_exit_code.should == 0
+end
 
 Then /^I am congratulated$/ do
   @last_result.should =~ /Congratulations!/
@@ -235,3 +238,8 @@ end
 Then /^I should see the following lines of output:$/ do |table|
   table.diff!([['blueprint'],['compass']])
 end
+
+Then /^I should see the following output: (.+)$/ do |expected|
+  (@last_result.strip + @last_error.strip).should == expected.gsub(/\$PROJECT_PATH/,Dir.pwd).strip
+end
+

lib/compass/commands/write_configuration.rb

@@ -20,7 +20,9 @@ module Compass
         opts.on("--debug [PROPERTY]", "Debug your configuration by printing out details.") do |prop|
           self.options[:debug] = prop.nil? ? true : prop.to_sym
         end
-
+        opts.on("-p PROPERTY", "--property PROPERTY", "Print out the value of the given property") do |prop|
+          self.options[:display] = prop.to_sym
+        end
         super
       end
     end
@@ -40,7 +42,13 @@ module Compass
       end
 
       def perform
-        if options[:debug]
+        if options[:display]
+          if Compass.configuration.respond_to?(options[:display])
+            puts Compass.configuration.send(options[:display])
+          else
+            raise Compass::Error, %Q{ERROR: configuration property '#{options[:display]}' does not exist}
+          end
+        elsif options[:debug]
           puts "Configuration sources:"
           c = Compass.configuration
           while c