Fix issue 93 Windows blob upload

[sunnycarter]

Fix for #93

Tested on Linux by writing unit test for parse_manifest and running it before and after change.
Tested on Window by trying to upload a blob with the path C:\blah\blah.json - failed before the fix, succeeds afterwards.

[vsoch]

Really nice job! If we get it fully working on Windows we will need to have a release for Windows for our conda recipe.

It looks like for linting, e.g.,:

python -m venv env
source env/bin/activate
pip install -r .github/dev-requirements.txt

Then

pre-commit run --all-files

Is hitting a few snags - mostly with typing if you want to adjust those.

 trim trailing whitespace.................................................Failed
- hook id: trailing-whitespace
- exit code: 1
- files were modified by this hook

Fixing oras/tests/test_utils.py
Fixing oras/tests/test_provider.py
Fixing oras/utils/fileio.py

mixed line ending........................................................Passed
black....................................................................Failed
- hook id: black
- files were modified by this hook

reformatted oras/utils/fileio.py

All done! ✨ 🍰 ✨
1 file reformatted, 13 files left unchanged.
All done! ✨ 🍰 ✨
13 files left unchanged.

isort....................................................................Failed
- hook id: isort
- files were modified by this hook

Fixing /home/runner/work/oras-py/oras-py/oras/tests/test_provider.py

mypy.....................................................................Failed
- hook id: mypy
- exit code: 1

oras/utils/fileio.py:364: error: Incompatible return value type (got "Tuple[str, ...]", expected "Tuple[str, Optional[str]]")
Found 1 error in 1 file (checked 14 source files)
oras/utils/fileio.py:364: error: Incompatible return value type (got "Tuple[str, ...]", expected "Tuple[str, Optional[str]]")
Found 1 error in 1 file (checked 13 source files)

flake8...................................................................Failed
- hook id: flake8
- exit code: 1

oras/utils/fileio.py:329:7: W605 invalid escape sequence '\m'
oras/utils/fileio.py:334:7: W605 invalid escape sequence '\m'

make: *** [Makefile:11: lint] Error 1
Error: Process completed with exit code 2.

[sunnycarter]

Thanks for the review. I had some issues with returning Tuples with Optional[str] in the type, so I've changed it to return a small class. All those checks are passing now.

[vsoch]

Thanks for fixing that, and sorry for the trouble! I have mixed feelings about "typing" in python - it seems to add more headache often than it's worth, but at least for this project we commit so makes sense to keep trying.

[sunnycarter]

Hi there, Thank you for merging this. Is it possible you can release oras 0.1.19? Sorry for hassling you if you were waiting until after the weekend to do it! Thanks Sunny

[vsoch]

Thank you for the reminder! I intended to but had two full days and just didn't get to it. 😆 https://github.com/oras-project/oras-py/releases/tag/0.1.19