CONDSTORE: STORE UNCHANGEDSINCE 0

[Alexey Melnikov <alexey.melnikov@xxxxxxxxx>]

I think the following text in section 3.2 of RFC 4551

>      Use of UNCHANGEDSINCE with a modification sequence of 0 always
>      fails if the metadata item exists.  A system flag MUST always be
>      considered existent, whether it was set or not.

is broken:

1) It is not clear why system flags have to be special
2) A flag existence is the same as have the flag set. Testing for flag 
existence can already be done using the FETCH (FLAGS) command.

There are two ways to fix it:

1). Remove the second sentence to remove special casing for system 
flags. This command would allow people to test if a particular flag or a 
set of flags is set on a message. However this would leave STORE -FLAGS 
UNCHANGEDSINCE somewhat meaningless.

2). Replace the second sentence to say that this command always fail 
with tagged NO for both system and user defined flags. Note that this 
doesn't affect annotations.

The rough consensus during the IMAPEXT meeting was to go with option 2.
If you have any objections to this, please speak up now.

Regards,
Alexey