main: Distinguish "preview" and "experimental" commands

Let's say package layering is "preview" - we show it in help, but
marked `(preview)`.

Whereas the `container` and `internals` builtins this patch calls
"experimental" - we don't show them in help even.

Both get a warning message when executed.

Closes: #354
Approved by: jlebon

src/app/main.c

@@ -32,19 +32,28 @@
 #include "rpmostree-builtins.h"
 
 #include "libgsystem.h"
+#include "libglnx.h"
 
-static RpmOstreeCommand commands[] = {
+static RpmOstreeCommand supported_commands[] = {
 #ifdef HAVE_COMPOSE_TOOLING
   { "compose", rpmostree_builtin_compose },
 #endif
   { "db", rpmostree_builtin_db },
   { "deploy", rpmostree_builtin_deploy },
-  { "pkg-add", rpmostree_builtin_pkg_add },
-  { "pkg-remove", rpmostree_builtin_pkg_remove },
   { "rebase", rpmostree_builtin_rebase },
   { "rollback", rpmostree_builtin_rollback },
   { "status", rpmostree_builtin_status },
   { "upgrade", rpmostree_builtin_upgrade },
+  { NULL }
+};
+
+static RpmOstreeCommand preview_commands[] = {
+  { "pkg-add", rpmostree_builtin_pkg_add },
+  { "pkg-remove", rpmostree_builtin_pkg_remove },
+  { NULL }
+};
+
+static RpmOstreeCommand experimental_commands[] = {
   { "internals", rpmostree_builtin_internals },
   { "container", rpmostree_builtin_container },
   { NULL }
@@ -68,7 +77,7 @@ static GOptionEntry daemon_entries[] = {
 static GOptionContext *
 option_context_new_with_commands (void)
 {
-  RpmOstreeCommand *command = commands;
+  RpmOstreeCommand *command = supported_commands;
   GOptionContext *context;
   GString *summary;
 
@@ -78,12 +87,14 @@ option_context_new_with_commands (void)
 
   while (command->name != NULL)
     {
-      /* Internals will remain hidden always, container will possibly
-       * get promoted at some point.  For now, it's an easter egg.
-       */
-      if (!g_str_equal (command->name, "internals")
-          && !g_str_equal (command->name, "container"))
-        g_string_append_printf (summary, "\n  %s", command->name);
+      g_string_append_printf (summary, "\n  %s", command->name);
+      command++;
+    }
+
+  command = preview_commands;
+  while (command->name != NULL)
+    {
+      g_string_append_printf (summary, "\n  %s (preview)", command->name);
       command++;
     }
 
@@ -177,6 +188,32 @@ on_sigint (gpointer user_data)
   return FALSE;
 }
 
+static RpmOstreeCommand *
+lookup_command_of_type (RpmOstreeCommand *commands,
+                        const char *name,
+                        const char *type)
+{
+  RpmOstreeCommand *command = commands;
+  const int is_tty = isatty (1);
+  const char *bold_prefix;
+  const char *bold_suffix;
+
+  bold_prefix = is_tty ? "\x1b[1m" : "";  
+  bold_suffix = is_tty ? "\x1b[0m" : "";
+
+  while (command->name)
+    {
+      if (g_strcmp0 (name, command->name) == 0)
+        {
+          if (type)
+            g_printerr ("%snotice%s: %s is %s command and subject to change.\n",
+                        bold_prefix, bold_suffix, name, type);
+          return command;
+        }
+      command++;
+    }
+  return NULL;
+}
 
 int
 main (int    argc,
@@ -232,15 +269,15 @@ main (int    argc,
   if (g_strcmp0 (command_name, "rpm") == 0)
     command_name = "db";
 
-  command = commands;
-  while (command->name)
-    {
-      if (g_strcmp0 (command_name, command->name) == 0)
-        break;
-      command++;
-    }
+  command = lookup_command_of_type (supported_commands, command_name, NULL);
 
-  if (!command->fn)
+  if (!command)
+    command = lookup_command_of_type (preview_commands, command_name, "a preview");
+
+  if (!command)
+    command = lookup_command_of_type (experimental_commands, command_name, "an experimental");
+
+  if (!command)
     {
       GOptionContext *context;
       gs_free char *help = NULL;