[p4] Propagating deleted files even if the file never existed in the target location

[Weeble]

(Apologies if this is a repost, I think I sent it with the wrong "From:"
header and it seems to have disappeared into a black hole.)

I've seen this pop up a few times when we've had some awkward
integrations across branches. In this scenario:

@1 Create file "mainline/foo"
@2 Integrate "mainline/..." to "branch_a/..." [creates branch_a/foo]
@3 Delete file "mainline/foo"
@4 Integrate "mainline/..." to "branch_b/..." [doesn't touch branch_b/foo]
@5 Integrate "branch_a/..." to "branch_b/..." [creates branch_b/foo]

...we have the file "foo" in branch_b even though we previously
integrated from a version of mainline that included the deletion. The
file won't be deleted until the *next* integration from mainline.

Is there any general way to do step 4 in a way that means that step 5
will not attempt to introduce the file? In this case it seems like we
could first branch from mainline/foo at 2 to branch_b/foo, to introduce
the file, then integrate again from mainline/foo to branch_b/foo to
delete the file. However, that gets pretty messy to do if many files
have been deleted, possibly over several changelists. Is there any way
to say "propagate file deletions even if the file never existed in the
target location"?