feat(git-node): auto-unshallow shallow clones

[aduh95]

NCU expects the local clone to not be shallow, and throws arguably confusing errors when running git node land on a shallow clone. We might pass the correct flag if we detect unshallowness.

For a concrete example, that would allow us to use shallow clone in the CQ, and lazy-unshallow only if there are PRs ready to land (currently, if there's a PRs that was open for more than 2 days, and CI is still running, it will cause CQ to fully clone the repo every 10 minutes for nothing).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.70%. Comparing base (ef135f5) to head (628d7c4).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #918   +/-   ##
=======================================
  Coverage   79.70%   79.70%           
=======================================
  Files          39       39           
  Lines        4642     4642           
=======================================
  Hits         3700     3700           
  Misses        942      942           

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