Listers are declared as plugins via the `swh.workers` entry_point.
As such, the registry function is expected to return a dict with the
`task_modules` field (as for generic worker plugins), plus:
- `lister`: the lister class,
- `models`: list of SQLAlchemy models used by this lister,
- `init` (optionnal): hook (callable) used to initialize the lister's state
(typically, create/initialize the database for this lister).
If not set, the default implementation creates database tables (after
optionally having deleted exisintg ones) according to models declared in
the `models` register field.
There is no need for explicitely add lister task modules in the main
`conftest` module, but any new/extra lister to be tested must be registered
(the tested lister module must be properly installed in the test environment).
Also refactor a bit the cli tools:
- add support for the standard --config-file option at the 'lister' group
level,
- move the --db-url to the 'lister' group,
- drop the --lister option for the `swh lister db-init` cli tool:
initializing (especially with --drop-tables) the database for a single
lister is unreliable, since all tables are created using a sibgle MetaData
(in the same namespace).
Simplify the code:
- do only inherit from ListerBase
- implement HTTP queries directly using requests
- get rid of convoluted code
Make the origin_url gathered from the git repo's "project" page instead of
building it from the 'url_prefix' hack. Now, the lister WILL make substancially
more requests, since it will make one request per listed git repo, but
the provided origin_url should be pretty reliable now.
When several url are provided as clonable URLs, choose the http/https one first,
otherwise, choose the first one of the list.
Add proper tests for the cgit lister.
Also, get rid of the 'time_updated' column in the model.
