Don't fail if a formula stub doesn't exist when checking Formula#outdated? by @Rylan12 in https://github.com/Homebrew/brew/pull/20948
Use formula stubs for shellcheck, shfmt, and actionlint operations in brew style by @Rylan12 in https://github.com/Homebrew/brew/pull/20949
dev-cmd/tests: remove HOMEBREW_USE_INTERNAL_API from test environment. by @MikeMcQuaid in https://github.com/Homebrew/brew/pull/20950
patches audit: add correctors by @Moisan in https://github.com/Homebrew/brew/pull/20943
Improvements to HOMEBREW_USE_INTERNAL_API by @Rylan12 in https://github.com/Homebrew/brew/pull/20947
Document HOMEBREW_USE_INTERNAL_API by @MikeMcQuaid in https://github.com/Homebrew/brew/pull/20951
github_runner_matrix: always deploy arm64 linux runner for bottling by @cho-m in https://github.com/Homebrew/brew/pull/20957
Add brew lgtm command to run multiple style checks in one command. by @MikeMcQuaid in https://github.com/Homebrew/brew/pull/20958
Bump the "all" group with 3 updates across multiple ecosystems by @dependabot[bot] in https://github.com/Homebrew/brew/pull/20961
download_queue: fix context bleeding out from threads. by @MikeMcQuaid in https://github.com/Homebrew/brew/pull/20962
resource_auditor: skip ftp.gnu.org audit by @cho-m in https://github.com/Homebrew/brew/pull/20964
checksum, version: improve .inspect output by @MikeMcQuaid in https://github.com/Homebrew/brew/pull/20965
dev-cmd/bump-cask-pr: add audit exceptions by @bevanjkay in https://github.com/Homebrew/brew/pull/20939

Full Changelog: https://github.com/Homebrew/brew/compare/4.6.19...4.6.20