[Geary] Labels vs Folders (and Gmail vs Other)

[Federico Bruni <fede inventati org>]

Hi folks

A few days ago I wrote a comment here:
https://bugzilla.gnome.org/show_bug.cgi?id=748973#c2

which should be probably discussed here. I'm curious to know what you 
think.

Labels is a concept which is really true only for Gmail server, which 
stores all conversations in one physical place (folder/dir) but can 
display them in multiple virtual places (labels) *without copying 
them*. That is why they call it labels and not folders. Because we 
should imagine the conversation as always being in the same "folder", 
and label is just a property of the conversation which allows it to 
appear in different places without actually moving on disk.

The other IMAP servers I know of don't work this way. They know only 
folders and a conversation can live in more than one folder only if 
it's copied (which makes the database grow).

Shouldn't Geary make a clear distinction?
If IMAP servers do not support labeling, Geary should not show labels 
for them.

Cheers
Federico