My understanding is that you don't "override" a command handler; here's
the right way to phrase it (or so I think): "org.eclipse.ui.edit.paste" is
a command id, this is defined by an extention of point
"org.eclipse.ui.commands"; now a command extension can have multiple
handlers, but at any given time only 0 or 1 may be activated.(see more at
http://wiki.eclipse.org/index.php/Platform_Command_Framework). What you
are looking for would be have your handler activated for command
"org.eclipse.ui.edit.paste". Unfortunately, as far as my research just
these two days goes, this is not possible if you have a retarget action
registered globally. The only way I can find to play nice with it is to
use the legacy action contribution approach, e.g. contribute an action
with id "paste", e.g. editorActions/viewActions or programmatically. I
even go as far as writing a handler to action bridge, but I can't figure
out a way to correctly control the enablement of the action bridged from
the handler.