Simplify gnt-os diagnose output

Currently, we always list the api/variants, even if these are empty.
This patch changes so that we make clear distiction for empty values
("[no variants]" versus "[variants: ]"), and we only list variants and
parameters when the OS API indicates they should be supported.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

scripts/gnt-os

@@ -29,6 +29,7 @@
 import sys
 
 from ganeti.cli import *
+from ganeti import constants
 from ganeti import opcodes
 from ganeti import utils
 
@@ -162,18 +163,30 @@ def DiagnoseOS(opts, args):
     for node_name, node_info in node_data.iteritems():
       nodes_hidden[node_name] = []
       if node_info: # at least one entry in the per-node list
-        (first_os_path, first_os_status, first_os_msg,
-         first_os_variants, _, first_os_api) = node_info.pop(0)
-        if not first_os_variants:
-          first_os_variants = []
-        first_os_msg = ("%s (path: %s) [variants: %s] [api: %s]" %
-                        (_OsStatus(first_os_status, first_os_msg),
-                         first_os_path, utils.CommaJoin(first_os_variants),
-                         utils.CommaJoin(first_os_api)))
-        if first_os_status:
-          nodes_valid[node_name] = first_os_msg
+        (fo_path, fo_status, fo_msg, fo_variants,
+         fo_params, fo_api) = node_info.pop(0)
+        fo_msg = "%s (path: %s)" % (_OsStatus(fo_status, fo_msg), fo_path)
+        if fo_api:
+          max_os_api = max(fo_api)
+          fo_msg += " [API versions: %s]" % utils.CommaJoin(fo_api)
         else:
-          nodes_bad[node_name] = first_os_msg
+          max_os_api = 0
+          fo_msg += " [no API versions declared]"
+        if max_os_api >= constants.OS_API_V15:
+          if fo_variants:
+            fo_msg += " [variants: %s]" % utils.CommaJoin(fo_variants)
+          else:
+            fo_msg += " [no variants]"
+        if max_os_api >= constants.OS_API_V20:
+          if fo_params:
+            fo_msg += (" [parameters: %s]" %
+                       utils.CommaJoin([v[0] for v in fo_params]))
+          else:
+            fo_msg += " [no parameters]"
+        if fo_status:
+          nodes_valid[node_name] = fo_msg
+        else:
+          nodes_bad[node_name] = fo_msg
         for hpath, hstatus, hmsg, _, _, _ in node_info:
           nodes_hidden[node_name].append("    [hidden] path: %s, status: %s" %
                                          (hpath, _OsStatus(hstatus, hmsg)))