Assert minimal copier version

[yajo]

The template needs a new key:

# copier.yml
_min_copier_version: v3.1.0

Otherwise the template might fail badly if a template is done for a version that i.e. includes #190 and is executed under a copier that doesn't have it.

@pawamoy You might be interested in this.

[pawamoy]

Yes, good catch, displaying a warning when the version is too low is way better than starting to generate and fail.

[yajo]

I'd say an error more than a warning... If the templater took the time to write this constraint, it's better to enforce it.

[pawamoy]

Unfortunately, I don't think it will be possible to write tests for that, because poetry-dynamic-versioning does not work with poetry run, and so we'll not be able to retrieve the current version to compare it to a _min_copier_version. Any workaround idea 😕 ? Maybe I could modify copier.__version__ myself in the tests 🤔

[yajo]

Mock it:

• https://docs.python.org/3/library/unittest.mock.html#unittest.mock.patch
• https://docs.pytest.org/en/latest/monkeypatch.html