Very recent Homebrew updates may fail with error messages about "shallow" clones. GitHub has requested this as these are said to be extremely expensive operations. Mitigations are discussed and the solution revealed here:
https://github.com/Homebrew/brew/pull/9383
https://github.com/Homebrew/discussions/discussions/225
https://github.com/Homebrew/discussions/discussions/226
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Homebrew revises update process at GitHub's request | Heykuki News