Hello again,

I've attached two patches:

1. Tests for the existing merge parameters function, based on your
   last edits to my previous patch.

2. A rewrite of the entire merge parameters function, with the new
   tangle sync actions.

   It's a big patch mostly, because there were no intermediate commits
   in which the org framework wouldn't be broken. Hope that's okay!

** Brief Explanation of (2)

This attempts to address the problem of having an :any keyword in a
mutually exclusive group such as:

#+begin_src elisp
   '((tangle yes no :any)
     (import export skip sync))
#+end_src

Since every parameter (e.g. "export") is tested against both of these
groups, and since a parameter that matches `:any' could be anything,
then a parameter like "export" will match in both groups.

To get around this, a merge strategy (see: `org-babel--merge-headers')
builds an alist of exclusion groups that a parameter could belong to.

e.g for a header with `:tangle myfile.txt skip' would give an alist of

#+begin_src elisp
  (setq params-alist '(("skip" "tangle" "import")
                       ("myfile.txt" "tangle")))
#+end_src

Note that the exclusion groups are referenced by the first element in
the group, acting as an alist key of sorts. This assumes that each
exclusion group has a unique car.

Parameters with two or more cdr elements are stripped of the exclusion
group that have the `:any' parameter (i.e. "tangle"), resulting in:

#+begin_src elisp
  (setq params-alist '(("skip" "import")
                       ("myfile.txt" "tangle")))
#+end_src

This alist is then inverted so that the group exclusion car becomes
the key, and rearranged so that it follows the order of exclusion
group definition (in this case, "tangle" group first then then
"import" group).

#+begin_src elisp
  (setq group-alist '(("tangle" "myfile.txt")
                      ("import" "skip")))
#+end_src

As the merge parameters function is called repeatedly for the same
header, this builds to hold the whole related hierarchy of the org:

#+begin_src org
  ,#+PROPERTIES: header-args :tangle topfile.txt import

  ,* One
  :PROPERTIES:
  :header-args: :tangle skip
  :END:

  ,#+begin_src bash :tangle myfile.txt

  ,#+end_src
#+end_src

 which would yield:

#+begin_src elisp
  (setq group-alist '(("tangle" "myfile.txt" "no" "topfile.txt")
                      ("import" "skip" "import")))
#+end_src

Assuming the hierarchy is given in the reverse order of this alist,
the correct action is then taken as the car of these groups:

   `:tangle myfile.txt skip'


** Problems

It seems to work well for most tests, except for the "file with
spaces.txt" which I'm not sure how to proceed with. I feel like
patching at the level `org-babel--merge-params' is the wrong way to
go, and that I should patch it further upstream.

That upstream leads to `org-babel-read' which currently chomps the
quotes off anything it gets:

#+begin_src elisp
  (org-babel-read " \"my file with quotes\" ")
#+end_src

I don't know if this is the expected behaviour for quoted strings with
spaces, so before I proceed trying to patch this I thought I would
check in with you and ask whether I should start patching here or not.


Best,
Mehmet