split-window-{right, below} not interchangeable with split-window-sensibly

[Tassilo Horn]

Hello,

I really like sensible window splitting, and basically I want to use it
almost everywhere.  (That's what split-window-preferred-function is for
which works just fine.)

However, there are modes like ediff that have their own
foo-split-window-fn defcustom.  There you can use both
split-window-{right,below}, but split-window-sensibly doesn't
necessarily work, because the former functions have an optional SIZE arg
while the latter has a mandatory WINDOW arg.

For example, ediff just does

    (funcall ediff-split-window-function)

and that clearly errors if its set to split-window-sensibly.
Internally, ediff somehow ignores the error and you end up with only one
buffer.

Wouldn't it make sense to have the same signatures for
split-window-sensibly and the other two functions so that they were
interchangeable?

Well, the SIZE arg is not too meaningful for split-window-sensibly as it
would mean either SIZE cols or lines...  So maybe just making its WINDOW
arg optional would suffice for almost all use-cases.

Bye,
Tassilo