create: detect URL from latest release if it isn't archive

Detects source archive for GitHub URL without version. Both releases
and tags share the same URL pattern for source archive

  https://github.com/Homebrew/brew/releases
  https://github.com/Homebrew/brew/tags

Library/Homebrew/formula_creator.rb

@@ -14,6 +14,9 @@ module Homebrew
     sig { returns(Version) }
     attr_reader :version
 
+    sig { returns(String) }
+    attr_reader :url
+
     sig { returns(T::Boolean) }
     attr_reader :head
 
@@ -79,6 +82,9 @@ module Homebrew
             latest_release = GitHub.get_latest_release(user, repository)
             version = Version.new(latest_release.fetch("tag_name"))
             odebug "github: version from latest_release: #{version}"
+
+            @url = "https://github.com/#{user}/#{repository}/archive/refs/tags/#{version}.tar.gz"
+            odebug "github: url changed to source archive #{@url}"
           rescue GitHub::API::HTTPNotFoundError
             odebug "github: latest_release lookup failed: #{url}"
           end

Library/Homebrew/test/formula_creator_spec.rb

@@ -41,6 +41,7 @@ RSpec.describe Homebrew::FormulaCreator do
         github_user_repository: ["buildpacks", "pack"],
         latest_release:         { "tag_name" => "v0.37.0" },
         expected_name:          "pack",
+        expected_url:           "https://github.com/buildpacks/pack/archive/refs/tags/v0.37.0.tar.gz",
         expected_version:       "v0.37.0",
       },
       "GitHub URL with name override":   {
@@ -69,6 +70,9 @@ RSpec.describe Homebrew::FormulaCreator do
         else
           expect(formula_creator.version).to be_null
         end
+        if (expected_url = test[:expected_url])
+          expect(formula_creator.url).to eq(expected_url)
+        end
         expect(formula_creator.head).to eq(test.fetch(:expected_head, false))
       end
     end