Feature: Skip .git folder in localdir client

[pnacht]

Is your feature request related to a problem? Please describe.
The localdir client currently runs through the repository's .git folder. This is a common folder which may (in rare cases) include many (or large, or many large) files which are irrelevant to Scorecard's analysis. Indeed, the issue in #3831 caused Scorecard to crash even when the "visible" large files were deleted.

Describe the solution you'd like
The localdir client simply skips the .git directory entirely.

Describe alternatives you've considered
With the changes @spencerschrock suggested in #3831 (comment), this may no longer be necessary to avoid crashing due to large "hidden" files, so this can simply be ignored once those changes have been made.

But the .git folder can still contain many files, which could slow Scorecard down by their sheer number.