Shipping discount gets evenly applied to all line items

[BoulderDave]

I just noticed that if you have a discount that is to be applied to
the shipping cost only, it will evenly disperse the discount across
all the order line items & including shipping (instead of just
shipping)

For example, if i have 2 line items and a shipping cost, and a
discount of $30 to be applied to shipping only, it will take $10 off
shipping, and $10 off each line item.

Also, if shipping is $0, it will take all $30 off the line items, and
nothing off shipping.

I'm using .9.2 but checked that the Discount.calc() function is the
same in trunk and it is.

Has anybody else experienced this issue or can someone else verify
that it exists?

[hynekcer]

@All users: Usefullness of the whole concept of splitting discount
equally to more items should be re-thought out. ($16 and $200 with
discount $30 is $1 and $185 and should be?)
WHO USE IT?

This did not work for long time also, I fixed it in
https://bitbucket.org/chris1610/satchmo/issue/1384
but I consider splitting discounts this way not too useful.

@BoulderDave:
Uncredible.
Yes, it is something obsoleted.
Before the changeset 494bf2a5224a (July 2009) there were two
checkboxes "Should shipping be included in the discount calculation?"
and "Should this discount remove all shipping costs?" which have been
replaced by listbox DISCOUNT_SHIPPING_CHOICES. One of options is
"Apply the discount above to shipping" which you probably use with
some of "all products" or "valid products" or "valid categories", so
the discount is also a little related to products.
The option value was internally named "INCLUDED" shortly, which have
been soon renamed to "APPLIED" but the code for action is still
unchanged. This is the cause.

@All: This were probably traces of the evolution of what is expected.
I do not want to fix anything before I know, what from builtin
discount methods is widely used or if customization is more usual and
more important or what is the most expected behaviour with current
discount data model. Many ideas for discussion are at the beginning of
issue https://bitbucket.org/chris1610/satchmo/issue/1381/ "Discount
System Brainstorm".

-- Hynek