Trouble with ocaml-dune and magic variables

[Julien Puydt <julien.puydt@gmail.com>]

Hi,

ocaml-dune does substitutions when building a project:
https://dune.readthedocs.io/en/latest/usage.html#dune-subst

and unfortunately, it is based on the version control system, so
tarballs obtained from a github release lack the necessary information
for this to work.

As a consequence, a package like elpi has to play sed tricks in its
debian/rules to do this:

https://salsa.debian.org/ocaml-team/elpi/-/blob/master/debian/rules?ref_type=heads

and now, trying to update the elpi package, I get breakages because
another file needs this trick (something I can fix... after much poking
around!) and because other things aren't built correctly. For example,
dune makes a META file which lacks the required "version = ..." line.

So I'm writing to this list either to rally people on looking for a
good solution or getting pointed to a fine manpage to read...

Cheers,

J.Puydt