Why doesn't DMD recreate folder structure when using multiple .d files and -H?

[Andrej Mitrovic]

For example:

$ dmd -H -o- atk/Action.d gio/DBusProxy.d -Hdinclude

Both files are written to the 'include' folder but they're flat
because the original folder structure is lost. So instead of having:

include/atk/Action.d
include/gio/DBusProxy.d

I have:
include/Action.d
include/DBusProxy.d

The files are completely unusable this way (and this happens
regardless of -Hd btw).
I didn't find an open bug report on this, but I think this is worthy
of an enhancement request.