Treat --depth like --collapse in register
Treat --depth like --collapse in register

Currently, collapsing is only done when both --depth and --collapse are
present.  This is very unintuitive and I have even stumbled over this
myself while implenting the feature.

Change --depth to behave just like --collapse in all cases (except that
--depth has a parameter associated.  --collapse defaults to 0 to retain
its old behavior).

afh/ledger,ledger/ledger,afh/ledger,ledger/ledger,ledger/ledger,afh/ledger,ledger/ledger,afh/ledger,ledger/ledger,afh/ledger