libnm: rework checkpoint API

The libnm API fir checkpoints was only introduced with 1.11. It
is not yet stable, so there is still time to adjust it. Note that
this changes API/ABI of the development branch.

Changes:

- we only add async variants of the checkpoint functions. I believe
  that synchronous D-Bus methods are fundamentally flawed, because
  they mess up the ordering of events.
  Rename the async functions by removing the "_async" suffix. This
  matches glib style, for which the async form is also not specially
  marked.

- for function that refere to a particular checkpoint (rollback and
  destroy), accept the D-Bus path as string, instead of an NMCheckpoint
  instance. This form is more flexible, because it allows to use
  the function without having a NMCheckpoint instance at hand. On the
  other hand, if one has a NMCheckpoint instance, he can trivially
  obtain the path to make the call.

examples/python/gi/checkpoint.py

@@ -46,6 +46,29 @@ def show(c, ts = None):
         print("  timeout: %u seconds%s" % (rt, "" if ts is None else (" (circa %s sec left)" % ((cr + (rt * 1000) - ts) / 1000.0))))
     print("  devices: %s" % (' '.join(sorted(map(lambda x: x.get_iface(), c.get_devices())))))
 
+def find_checkpoint(client, path):
+    for c in client.get_checkpoints():
+        if c.get_path() == path:
+            return c
+    return None
+
+def validate_path(path, client):
+    try:
+        num = int(path)
+        path = "/org/freedesktop/NetworkManager/Checkpoint/%u" % (num)
+    except Exception as e:
+        pass
+
+    if not path or path[0] != '/':
+        sys.exit('Invalid checkpoint path \"%s\"' % (path))
+
+    if client is not None:
+        checkpoint = find_checkpoint(client, path)
+        if checkpoint is None:
+            print('WARNING: no checkpoint with path "%s" found' % (path))
+
+    return path
+
 def do_create(client):
     flags = NM.CheckpointCreateFlags.NONE
     if len(sys.argv) < 3:
@@ -76,27 +99,13 @@ def do_create(client):
             sys.stderr.write("Failed: %s\n" % e.message)
         main_loop.quit()
 
-    client.checkpoint_create_async(devices, timeout, flags, None, create_cb, None)
-
-def find_checkpoint(client, arg):
-    try:
-        num = int(arg)
-        path = "/org/freedesktop/NetworkManager/Checkpoint/%u" % num
-    except Exception as e:
-        path = arg
-
-    for c in client.get_checkpoints():
-        if c.get_path() == path:
-            return c
-    return None
+    client.checkpoint_create(devices, timeout, flags, None, create_cb, None)
 
 def do_destroy(client):
     if len(sys.argv) < 3:
         sys.exit("Missing checkpoint path")
 
-    checkpoint = find_checkpoint(client, sys.argv[2])
-    if checkpoint is None:
-        sys.exit("Unknown checkpoint %s" % sys.argv[2])
+    path = validate_path(sys.argv[2], client)
 
     def destroy_cb(client, result, data):
         try:
@@ -106,15 +115,13 @@ def do_destroy(client):
             sys.stderr.write("Failed: %s\n" % e.message)
         main_loop.quit()
 
-    client.checkpoint_destroy_async(checkpoint, None, destroy_cb, None)
+    client.checkpoint_destroy(path, None, destroy_cb, None)
 
 def do_rollback(client):
     if len(sys.argv) < 3:
         sys.exit("Missing checkpoint path")
 
-    checkpoint = find_checkpoint(client, sys.argv[2])
-    if checkpoint is None:
-        sys.exit("Unknown checkpoint %s" % sys.argv[2])
+    path = validate_path(sys.argv[2], client)
 
     def rollback_cb(client, result, data):
         try:
@@ -130,7 +137,7 @@ def do_rollback(client):
             sys.stderr.write("Failed: %s\n" % e.message)
         main_loop.quit()
 
-    client.checkpoint_rollback_async(checkpoint, None, rollback_cb, None)
+    client.checkpoint_rollback(path, None, rollback_cb, None)
 
 def do_adjust_rollback_timeout(client):
     if len(sys.argv) < 3:
@@ -142,9 +149,7 @@ def do_adjust_rollback_timeout(client):
     except:
         sys.exit("Invalid timeout")
 
-    checkpoint = find_checkpoint(client, sys.argv[2])
-    if checkpoint is None:
-        sys.exit("Unknown checkpoint %s" % sys.argv[2])
+    path = validate_path(sys.argv[2], client)
 
     def adjust_rollback_timeout_cb(client, result, data):
         try:
@@ -154,7 +159,7 @@ def do_adjust_rollback_timeout(client):
             sys.stderr.write("Failed: %s\n" % e.message)
         main_loop.quit()
 
-    client.checkpoint_adjust_rollback_timeout(checkpoint.get_path(), add_timeout, None, adjust_rollback_timeout_cb, None)
+    client.checkpoint_adjust_rollback_timeout(path, add_timeout, None, adjust_rollback_timeout_cb, None)
 
 def do_show(client):
     ts = nmex.nm_boot_time_ms()