_to_relative_path to support mixing slashes and backslashes

[Andrej730]

Working on Windows you sometime end up having some paths with backslashes (windows native) and some with slashes - this PR will resolve the issue using gitpython for those kind of cases (see example below). It will also fix the issues if paths contain redundant separators or "..".

import git

repo = git.Repo(r"C:\gittest")
repo.index.add(r"C:\gittest\1.txt")
# Traceback (most recent call last):
#   File "c:\second_test.py", line 5, in <module>
#     repo.index.add(r"C:/gittest/2.txt")
#   File "Python311\Lib\site-packages\git\index\base.py", line 879, in add
#     paths, entries = self._preprocess_add_items(items)
#                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
#   File "Python311\Lib\site-packages\git\index\base.py", line 672, in _preprocess_add_items
#     paths.append(self._to_relative_path(item))
#                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
#   File "Python311\Lib\site-packages\git\index\base.py", line 657, in _to_relative_path
#     raise ValueError("Absolute path %r is not in git repository at %r" % (path, self.repo.working_tree_dir))
# ValueError: Absolute path 'C:/gittest/2.txt' is not in git repository at 'C:\\gittest'

repo.index.add(r"C:/gittest/2.txt")

repo.index.commit("test")

[Byron]

Thanks a lot - this looks like an improvement.

Could you also add a test that fails with the previous implementation?

Maybe as a question on the side: what prevents the caller from normalizing the input paths right away?

[Andrej730]

Could you also add a test that fails with the previous implementation?

Added.

Maybe as a question on the side: what prevents the caller from normalizing the input paths right away?

Well, normalizing the inputs is one error traceback back away indeed but usually when some method has a string-path argument user expects the method to handle any kind of paths.

[Byron]

Thanks for the test!

Once CI passes I think this can be merged.

[Byron]

Thanks a lot!