`gitdir` overwrites files without confirmation

[alichtman]

Thanks for this tool! I accidentally overwrote some of my files earlier, and I think this is a preventable mistake.

https://github.com/sdushantha/gitdir/blob/0c071cca295907df216c93251803f5076cd82165/gitdir/gitdir.py#L103C17-L103C43

You can reproduce the problem with:

$ cd /tmp

$ gitdir https://github.com/sdushantha/gitdir/tree/master/gitdir
Downloaded: __init__.py
Downloaded: __main__.py
Downloaded: gitdir.py
✔ Download complete

$ echo "will be deleted" > gitdir/__main__.py

$ gitdir https://github.com/sdushantha/gitdir/tree/master/gitdir
Downloaded: __init__.py
Downloaded: __main__.py
Downloaded: gitdir.py
✔ Download complete

$ head gitdir/__main__.py
from .gitdir import main

main()

I'd propose adding a prompt to confirm, and a --force,-f flag