shell auto completions for project specific values

[martin-schulze-e2m]

Issue Kind

Brand new capability

Description

The current completions allow for finding commands and their flags (e.g. poetry install --all-extras), but they don't help with project specific values like package or group names.

For example, poetry install --with should offer all known groups as completion or poetry update or poetry show should offer names of all packages in poetry.lock. I am sure there are more examples.

For comparison, take git checkout, which offers a list of all available branches as suggested completions.

Impact

Having this information not available requires context switches to find them. Typos and unexpected package names make the process harder than it needs to be. Cutting down the feedback time often has compounding effects.

Workarounds

The information is available in pyproject.toml/poetry.lock and through querying commands like poetry show.