That is a completion which is aware of what it should complete.
Currently only account names are supported.
When you insert an account name like this:
Asse<C-X><C-O>
You will get a list of top-level accounts that start like this.
Go ahead and try something like:
As:Ban:Che<C-X><C-O>
When you have an account like this, 'Assets:Bank:Checking'
should show up.
This helps to avoid confusion when an account is not
seperated from the amount by two spaces or a tab but only by one space.
In these cases the amount will now be highlighted
as if it belongs to the account name.
Thanks to user 'plaindocs' for reporting this.
