qubes/app: automatically enable offline mode when running in chroot

Do not spray --offline-mode over every installer-related script.

QubesOS/qubes-issues#2412

qubes/app.py

@@ -135,10 +135,18 @@ class VirConnectWrapper(object):
 class VMMConnection(object):
     '''Connection to Virtual Machine Manager (libvirt)'''
 
-    def __init__(self, offline_mode=False):
+    def __init__(self, offline_mode=None):
+        '''
+
+        :param offline_mode: enable/disable offline mode; default is to
+        enable when running in chroot as root, otherwise disable
+        '''
         self._libvirt_conn = None
         self._xs = None
         self._xc = None
+        if offline_mode is None:
+            offline_mode = bool(os.getuid() == 0 and
+                os.stat('/') != os.stat('/proc/1/root/.'))
         self._offline_mode = offline_mode
 
     @property
@@ -600,7 +608,7 @@ class Qubes(qubes.PropertyHolder):
         default=True,
         doc='check for updates inside qubes')
 
-    def __init__(self, store=None, load=True, offline_mode=False, lock=False,
+    def __init__(self, store=None, load=True, offline_mode=None, lock=False,
             **kwargs):
         #: logger instance for logging global messages
         self.log = logging.getLogger('app')

qubes/tools/__init__.py

@@ -333,7 +333,7 @@ class QubesArgumentParser(argparse.ArgumentParser):
             self.add_argument('--qubesxml', metavar='FILE', action='store',
                               dest='app', help=argparse.SUPPRESS)
             self.add_argument('--offline-mode', action='store_true',
-                default=False, dest='offline_mode', help=argparse.SUPPRESS)
+                default=None, dest='offline_mode', help=argparse.SUPPRESS)
 
 
         self.add_argument('--verbose', '-v', action='count',