- Use separate functions for successive passes in module `Driver.Passes`
- Use other functions for end results printing in module `Driver.Commands`
As a consequence, it is much more flexible to use by plugins or libs and we no
longer need the complex polymorphic variant parameter.
This patch leverages previous changes to use Cmdliner subcommands and
effectively specialises the flags of each Catala subcommand.
Other changes include:
- an attempt to normalise the generic options and reduce the number of global
references. Some are ok, like `debug` ; some would better be further cleaned up,
e.g. the ones used by Proof backend were moved to a `Proof.globals` module and
need discussion. The printer no longer relies on the global languages and prints
money amounts in an agnostic way.
- the plugin directory is automatically guessed and loaded even in dev setups.
Plugins are shown by the main `catala` command and listed in `catala --help`
- exception catching at the toplevel has been refactored a bit as well; return
codes are normalised to follow the manpage and avoid codes >= 128 that are
generally reserved for shells.
Update tests
The upside of this is that each command can define specific flags ; there is a
small loss of backwards-compatibility in that the command needs to be the first
argument.
`catala --help` will now only show a summary of commands, with more specific
manpages shown on `catala CMD --help`.
Another point is that the plugin interface is extended to allow plugins to be
registered as subcommands and have their own flags (this will be very useful for
adding flags to the lazy/dot/explanation plugin that has many options).
Note that no efforts has yet been made to specialise the options, the previous
type was just made global for all subcommands.
To try it (without installing Catala):
```shell-session
$ make plugins
$ export CATALA_PLUGINS=_build/default/compiler/plugins
$ dune exec -- catala lazy examples/aides_logement/tests/tests_calcul_apl_locatif.catala_fr -s Exemple2
```
Keep in mind that this is a work-in-progress prototype :)
It's not expected to stay that way forever, but some additional effort will be required for them to preserve (or restore) types; until then, be safe and don't forward possibly incorrect information.
