[Dune] dunecontrol and configure

[Christian Engwer]

Hi,

currently the developer of a module has to specify the dependencies of
the module at two places:

1) dune.module
  Here it is sufficient to specify the direct dependencies, i.e. you
  saythat you need dune-grid and recursively dune-common in required
  as well.
2) configure.ac
  Here one has provide the whole list of dependencies, in the _correct
  order_. This can get anoiing once you have bigger projects with more
  dependencies. Also all (potential) modules mut be known by
  dune-common.

I did some experiments with m4 and now I'm already able to determin
the direct dependecies by parsing dune.module and using this
information during the creation of configure. What doesn't work is the
recursive evaluation of the dependencies. In order to get this feature
to work, I would have to change the way dunecontrol works.

My suggestion is to add an environment variable DUNECONTROLPATH with a
colon sperated list of directories. Each entry in this variable is
search recursively for dune.module files.

When such a variable is defined, it doesn't matter where you invoke
dunecontrol, as it will always find the same module. Therefor it can
also be called from inside one of the modules during the autoconf
call.

I could write dunecontrol in such a way that, if now path is specified
'.' is used. When autogen.sh is called from dunecontrol, dunecontrol
could again set the environment variable.

Please give me feedback on this issue. Should I add this change?

Christian