I have a problem: we are using a package that is not maintained for a while now. So we forked it in order to maintain it ourselves. The package already exists lets say it is named package_a. Most of the code and the __init__ are in the package_a/ folder.
Now we want to make our own package that will include our maintained code and we want to name is package_b. So far so good but the problems is that package_b wants to have the code and the __init__ in package_b/ folder and github changes the contributions for all files when a folder is renamed. And I would like that credit for contributions stays where it is due, the 10k+ lines of code didn't just appear in my local repo out of thin air. Any suggestions how we can have package named package_b but keep the code in the original folder package_a/?
I am thinking along the lines of trying with some clever way of importing package_a into package_b or something along the line but I hope for a definite answer.
Instead of copying the code or trying to import A into B, extract the common code into a 3rd package which both A and B import. Or perhaps a subclass. This doesn't solve your contribution problem, but it does avoid making a big maintenance hassle by copying and pasting 10,000 lines of code.

Git doesn't record copies and renames, but it can recognize when they happen. To give Git the best chance of recognizing a copy, do only the copy in its own commit. Make no changes to the content. Then in a second commit make any necessary changes to the copied code.
In normal Git you can nudge git log and git blame to honor copies and renames with -C. Git doesn't do this by default because it's more expensive.
Github will do what Github will do.
Regardless of who Github says who wrote what line their contributions will still be in the project history. That's how it goes. You make your contribution and then others put their own work on top of it. This is normal. Their contributions remain in the history.
"History sheer" is also normal, that's when a change touches many lines but is otherwise insignificant. For example, if you were to restyle the code that would cause a history sheer. git blame will say that was the last commit to touch the code. git blame -w mitigates this somewhat, and Github has an "ignore whitespace" option. History sheer is normal and so is learning to skip over it.
The tools work for us. Don't bend yourself for the benefit of the tools.
If you want to make a special shout out to your contributors, make a contributor's section to your README.md.
Rename folder in git without changing the contributors