tools: drop --delete and --unset aliases for --default option

This may be confiusing, for example one may think that
`qvm-prefs --unset vmname netvm` will make vmname network-disconnected.
This type of mistakes may have severe security consequence, so better
drop those option names.

QubesOS/qubes-issues#3002

cc @rootkovska

doc/manpages/qubes-prefs.rst

@@ -6,7 +6,7 @@
 Synopsis
 --------
 
-:command:`qubes-prefs` [-h] [--verbose] [--quiet] [--force-root] [--help-properties] [*PROPERTY* [*VALUE*\|--delete]]
+:command:`qubes-prefs` [-h] [--verbose] [--quiet] [--force-root] [--help-properties] [*PROPERTY* [*VALUE*\|--default]]
 
 Options
 -------
@@ -27,9 +27,9 @@ Options
 
    Decrease verbosity.
 
-.. option:: --unset, --default, --delete, -D
+.. option:: --default, -D
 
-   Unset the property. If is has default value, it will be used instead.
+   Reset propety to default value.
 
 .. option:: --get, -g
 

doc/manpages/qvm-prefs.rst

@@ -6,7 +6,7 @@
 Synopsis
 --------
 
-:command:`qvm-prefs` qvm-prefs [-h] [--verbose] [--quiet] [--force-root] [--help-properties] *VMNAME* [*PROPERTY* [*VALUE* \| --delete \| --default ]]
+:command:`qvm-prefs` qvm-prefs [-h] [--verbose] [--quiet] [--force-root] [--help-properties] *VMNAME* [*PROPERTY* [*VALUE* \| --default ]]
 
 Options
 -------
@@ -27,9 +27,9 @@ Options
 
    Decrease verbosity.
 
-.. option:: --unset, --default, --delete, -D
+.. option:: --default, -D
 
-   Unset the property. If is has default value, it will be used instead.
+   Reset property to its default value.
 
 .. option:: --get, -g
 

qubesadmin/tools/qubes_prefs.py

@@ -20,7 +20,6 @@
 
 ''' Manipulate global properties.'''
 
-# TODO merge printing with qvm-prefs
 # TODO list only non-default properties
 
 from __future__ import print_function

qubesadmin/tools/qvm_prefs.py

@@ -59,11 +59,10 @@ def get_parser(vmname_nargs=1):
         nargs='?',
         help='new value of the property')
 
-    parser.add_argument('--unset', '--default', '--delete', '-D',
+    parser.add_argument('--default', '-D',
         dest='delete',
         action='store_true',
-        help='unset the property; '
-             'if property has default value, it will be used instead')
+        help='reset property to its default value')
 
     return parser