generate-advisories-api: add advisory index generator

[p-linnane]

brew generate-advisories-api builds the concatenated BREW-* advisory index for formulae.brew.sh from a checkout of Homebrew/advisory-database, mirroring that repository's AdvisoryIndex (kept in step): matched records without a comparable range are skipped, output is grouped by formula and deterministic, and mixed schema versions fail the build.

This is the first half of serving the index from formulae.brew.sh/api instead of a raw git URL: the site's CI gains a generate-advisories job running this command, after which brew vulns flips its DATA_URL and Homebrew/advisory-database stops committing the 67 MB generated file. Output was verified byte-identical to the existing rake advisories:concat over the full 20,918-record corpus.

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• I did not use AI/LLM to create this PR, or I disclosed the tool/model below and reviewed its output; I did not attribute commits to AI and will answer maintainer questions and review comments myself without AI/LLM.

AI disclosure: drafted with Claude Code under my direction. I reviewed the diff and verified it locally with brew style, brew typecheck and brew lgtm, including byte-identical output against the existing generator; commits are authored and signed off by me with no AI attribution, and review responses will be my own.

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[Copilot]

Pull request overview

Adds a new developer-only command, brew generate-advisories-api, to generate a deterministic, formula-grouped advisory index JSON for formulae.brew.sh from a Homebrew/advisory-database checkout. This supports migrating the advisory index away from a raw git URL and towards being served via the formulae.brew.sh API.

Changes:

• Introduces Homebrew::DevCmd::GenerateAdvisoriesApi to build api/advisories.json from advisory-database records, including filtering/ordering and schema-version consistency checks.
• Adds RSpec coverage for grouping/filtering/determinism and mixed schema-version failure.
• Updates shell completion scripts (bash/fish/zsh) and adds the Sorbet RBI for the new dev command.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
Library/Homebrew/dev-cmd/generate-advisories-api.rb	Implements the new advisory index generator command and filtering/ordering logic.
Library/Homebrew/test/dev-cmd/generate-advisories-api_spec.rb	Adds tests for deterministic grouped output and mixed schema-version failure.
Library/Homebrew/sorbet/rbi/dsl/homebrew/dev_cmd/generate_advisories_api.rbi	Adds Tapioca-generated RBI for the new dev command’s dynamic args method.
completions/bash/brew	Registers the command and adds option completion for bash.
completions/fish/brew.fish	Registers the command and adds option completion for fish.
completions/zsh/_brew	Registers the command and adds option completion for zsh.

Files not reviewed (1)

• Library/Homebrew/sorbet/rbi/dsl/homebrew/dev_cmd/generate_advisories_api.rbi: File type not supported

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[MikeMcQuaid]

Makes sense! For both this and analytics: would be nice to be able to skip from regenerating every 15m and have a cache to fall back on? Not a blocker.

[p-linnane]

Good idea. I will add those in follow up PRs.