babel default header args as functions

[Matt Huszagh]

I've added the ability in my own configuration to use lambda functions
that evaluate to a string as babel default header arguments, instead of
just the plain strings currently allowed. Would anyone else be
interested in this feature? Shall I prepare a patch?

There are a number of use cases for this, but to give you an idea,
here's one I'm using myself.

  (setq org-babel-default-header-args:latex
        `((:file . (lambda ()
                     (concat "img/"
                             (sha1 (org-element-property :value 
(org-element-at-point)))
                             (by-backend '((html . "-html") (t . "-org")))
                             ".svg")))))

This computes a filename based on the hash of the block contents.

Matt