configparser.NoOptionError if submodule's URL key name is Url rather than url in .gitmodules

[frezcirno]

Hi, thanks for your effort in this excellent library.

Recently, I'm mining many OSS repositories using GitPython, it's a handy tool and helps me a lot. And I encountered a weird error when processing this repository.

The minimal code to reproduce the error is:

import git

# git clone https://github.com/zoneminder/zoneminder.git zoneminder
repo = git.Repo("zoneminder")

repo.submodules  # <--- This line causes the error

And the exception is:

Traceback (most recent call last):
  File "/home/frezcirno/test.py", line 6, in <module>
    gitrepo.submodules  # <-- this line causes the error
    ^^^^^^^^^^^^^^^^^^
  File "/home/frezcirno/miniconda3/envs/work/lib/python3.11/site-packages/git/repo/base.py", line 422, in submodules
    return Submodule.list_items(self)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/frezcirno/miniconda3/envs/work/lib/python3.11/site-packages/git/util.py", line 1189, in list_items
    out_list.extend(cls.iter_items(repo, *args, **kwargs))
  File "/home/frezcirno/miniconda3/envs/work/lib/python3.11/site-packages/git/objects/submodule/base.py", line 1382, in iter_items
    u = parser.get(sms, "url")
        ^^^^^^^^^^^^^^^^^^^^^^
  File "/home/frezcirno/miniconda3/envs/work/lib/python3.11/site-packages/git/config.py", line 122, in assure_data_present
    return func(self, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/frezcirno/miniconda3/envs/work/lib/python3.11/configparser.py", line 808, in get
    raise NoOptionError(option, section)
configparser.NoOptionError: No option 'url' in section: 'submodule "web/api/app/Plugin/CakePHP-Enum-Behavior"'

It seems that the root cause is the .gitmodule file in this repository contains a Url instead of url key, which interferes GitPython's parsing process. As a result, commit diff is also unusable.

As the .gitmodule with Url can be correctly recognized by git, would this be a small bug?

[Byron]

Thanks for reporting. The submodules implementation is definitely not according to specification and it's more a matter of luck if it works. Maybe issues like these that seem to be about capitalization can be fixed though, and I invite contributions.