rebasing, git-am and whitespace cleanup conundrims

Hola!

i'm going through a rebase of a long series of patches (~50) that have
quite a bit of trailing whitespace. Once the rebase is done on my repo
(resolving all the code level conflicts), I want to re-rebase it on
top of the same commit but cleaning up trailing whitespace.

The problem is that upstream has 'some' trailing whitespace. The
policy is to reject "new" trailing whitespace and cleanup in stages to
avoid big merge conflicts and stuff.

Now, once the early patches are "in" with --whitespace=trim, the
following patches don't apply anymore :-/ and I can't just trim
whitespace in the whole patch series automatically.

Is there any way to get git-apply to ignore whitespace differences
when applying like GNU patch -l?

When -3 is passed, it must be calling the merge utility from
merge_file() -- which doesn't do 'ignore-whitespace'. But if it's a
straight patch application, it should be possible to do something like
that... maybe?

cheers,