Faster folder switching
I'm using Geary on a slow IMAP server that has a lot of folders. Switching folders typically takes around a minute for me.
Some simple tracing showed that rebuilding {copy,move}_folder_menu takes up the vast majority of this, simply because it asks the server for the full folder-list again.
We can easily do slightly better here, by only doing this when switching accounts.
An even better would be to cache a current list of folders (with some background-synchronization with the server), and using that instead of fetching. But I'll leave that for another day.
This brings the folder-switching time down to pretty much unnoticeable for me... unless I switch accounts ;)