[console] Allow showing properties from command line.

* sources/environment/commands/properties.dylan
  (parse-next-argument on <command-property>): New method for parsing
    an argument and converting it to a <command-property>.

* sources/environment/console/command-line.dylan
  (class <basic-main-command>): Add slot for %show.
  (do-execute-command): Handle -show being passed by invoking the
    show property command.

* sources/environment/console/compiler-command-line.dylan
  (command-line main): Add new show keyword parameter.

* sources/environment/console/environment-command-line.dylan
  (command-line main): Add new show keyword parameter.

sources/environment/commands/properties.dylan

@@ -20,6 +20,19 @@ define method parameter-type-name
   "property"
 end method parameter-type-name;
 
+define method parse-next-argument
+    (context :: <server-context>, type == <command-property>, text :: <string>,
+     #key start :: <integer> = 0, end: stop = #f)
+ => (value :: <command-property>, next-index :: <integer>)
+  let (name, next-index)
+    = parse-next-word(text, start: start, end: stop);
+  if (name)
+    values(find-named-property(context, as(<symbol>, name)), next-index)
+  else
+    parse-error("Missing keyword argument")
+  end
+end method parse-next-argument;
+
 define open generic ensure-property-available
     (context :: <server-context>, property :: <command-property>)
  => ();

sources/environment/console/command-line.dylan

@@ -19,6 +19,8 @@ define abstract class <basic-main-command> (<basic-command>)
     init-keyword: internal-debug:;
   constant slot %project :: false-or(<file-locator>) = #f,
     init-keyword: project:;
+  constant slot %show           :: false-or(<command-property>) = #f,
+    init-keyword: show:;
   constant slot %help?          :: <boolean> = #f,
     init-keyword: help?:;
   constant slot %logo?          :: <boolean> = #f,
@@ -169,6 +171,8 @@ define method do-execute-command
       run(<version-command>)
     elseif (command.%shortversion?)
       run(<version-command>, short: "short")
+    elseif (command.%show)
+      run(<show-property-command>, property: command.%show);
     else
       command.%logo? & message(context, dylan-banner());
       let personal-root = command.%personal-root;

sources/environment/console/compiler-command-line.dylan

@@ -28,6 +28,8 @@ define command-line main => <main-command>
   flag echo-input       = "echoes all input to the console";
   flag verbose          = "show verbose output";
 
+  keyword show :: <command-property> = "show a compiler setting";
+
   flag import           = "import the project";
   flag build            = "build the project";
   flag compile          = "compile the project";

sources/environment/console/environment-command-line.dylan

@@ -103,6 +103,8 @@ define command-line main => <main-command>
   flag debugger         = "enter the debugger if this program crashes";
   flag echo-input       = "echoes all input to the console";
 
+  keyword show :: <command-property> = "show a compiler setting";
+
   flag import           = "import the project";
   flag build            = "build the project";
   flag compile          = "compile the project";