api: add using: attribute to head & stable URLs

[EricFromCanada]

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---

Some formulae rely on the using: attribute to indicate how a resource is to be downloaded if it can't be detected via the domain name or protocol, e.g.:

• libvorbis's stable URL has using: :homebrew_curl as it's hosted on a TLS-1.3-only server
• trino's stable URL has using: :nounzip to allow for manual hard-link-preserving decompression
• the head URLs for abcl, global, nginx, objfw, squid each have a using attribute to indicate the VCS needed to fetch their sources

This change allows from-source installations of these and similar formulae to work when using the API.

Current output:

$ brew info --json pytouhou | jq .[0].urls
{
  "stable": {
    "url": "https://hg.linkmauve.fr/touhou",
    "tag": null,
    "revision": "5270c34b4c00",
    "checksum": null
  },
  "head": {
    "url": "https://hg.linkmauve.fr/touhou",
    "branch": null
  }
}

$ brew fetch --HEAD blastem
==> Downloading https://www.retrodev.com/repos/blastem
##################################################################################################################################################################### 100.0%
Downloaded to: /Users/eric/Library/Caches/Homebrew/downloads/ae00afc1c31ad2cdd9ef6e4ea0876edc8206c3c47c11a628a8593d838242aca5--blastem
SHA256: 72b87d3a585b96e977f9f29cf6fcd9dcee0e9026fc3c69d0b9fdb16b35e679e9
# this just downloads a web page

Future:

$ HOMEBREW_NO_INSTALL_FROM_API=1 brew info --json pytouhou | jq .[0].urls
{
  "stable": {
    "url": "https://hg.linkmauve.fr/touhou",
    "tag": null,
    "revision": "5270c34b4c00",
    "checksum": null,
    "using": "hg"
  },
  "head": {
    "url": "https://hg.linkmauve.fr/touhou",
    "branch": null,
    "using": "hg"
  }
}

$ HOMEBREW_NO_INSTALL_FROM_API=1 brew fetch --HEAD blastem
==> Cloning https://www.retrodev.com/repos/blastem
requesting all changes
adding changesets
adding manifests
adding file changes
added 2346 changesets with 5011 changes to 324 files (+1 heads)
new changesets 2432d177e1ac:c76c81c21ae5
updating to branch default
300 files updated, 0 files merged, 0 files removed, 0 files unresolved
Resource: vasm
==> Downloading http://phoenix.owl.de/tags/vasm1_8i.tar.gz
##################################################################################################################################################################### 100.0%
Downloaded to: /Users/eric/Library/Caches/Homebrew/downloads/4f31e8fb49321255218db07092e8864e9e036e14c2c563c1add9ea1201164d99--vasm1_8i.tar.gz
SHA256: 9ae0b37bca11cae5cf00e4d47e7225737bdaec4028e4db2a501b4eca7df8639d
==> Downloading https://www.retrodev.com/repos/blastem/raw-rev/dbbf0100f249
##################################################################################################################################################################### 100.0%
Downloaded to: /Users/eric/Library/Caches/Homebrew/downloads/70a17ee109695d03f5ece64dd949f1b08371b9e3592a96d1738aac5868fba8c3--dbbf0100f249
SHA256: e332764bfa08e08e0f9cbbebefe73b88adb99a1e96a77a16a0aeeae827ac72ff

[Bo98]

Will need adding here too:

brew/Library/Homebrew/formulary.rb

Line 244 in 0932f36

url_spec = { tag: urls_stable["tag"], revision: urls_stable["revision"] }.compact

plus the equivalent a few lines down for head

[Bo98]

using can be a Class and we're probably not going to ever support that, nor do we need to for Homebrew/core.

Suggested change

	"using" => stable_spec.using,
	"using" => (stable_spec.using if stable_spec.using.is_a?(Symbol)),

(+ same change to head)

[Bo98]

Suggested change

	using: urls_stable["using"],
	using: urls_stable["using"]&.to_sym,

(+ same change to head)

[MikeMcQuaid]

Thanks @EricFromCanada!