ogrinfo() does not validate num_features, so None and negative values give surprising results

[Caleb Jeffery Teye]

django.contrib.gis.utils.ogrinfo(data_source, num_features=10) is documented (and named) as taking the number of features to display per layer. Internally, it passes the argument straight into a list slice:

# django/contrib/gis/utils/ogrinfo.py
for j, feature in enumerate(layer[:num_features]):

...

Because the value isn't validated, Python's slicing rules leak through and produce results that don't match what the parameter name implies:

from django.contrib.gis.utils import ogrinfo
ogrinfo("cities.shp", num_features=None) # prints *every* feature, not none
ogrinfo("cities.shp", num_features=-2) # prints all features except the last two

A caller reasonably expecting num_features to mean "how many features to show" gets neither an error nor the requested count.

ogrinfo is exported in all, so this is public API. The fix should decide on the intended contract — most likely validating that num_features is a non-negative integer and raising TypeError/ValueError otherwise — and add tests. Any change in behaviour for None/negative input should be weighed for backwards compatibility (possibly a deprecation path).

Spotted while documenting ogrinfo() in #25927 — see the review discussion on ​PR #21443.