When not using cleartool, external update invokes
clearviewupdate separately for each selected project.
It is probably more convenient to run it once with all
projects on the command-line, because e.g. it allows to
click on "Show details" once and see the results of the
Attached patch makes clearviewupdate to be invoked once
with all selected projects. It is to be applied against
HEAD (as of 2005-06-14).