Restore support for catalina

Fix typo

Library/Homebrew/os/mac/version.rb

@@ -0,0 +1,107 @@
+# typed: true
+# frozen_string_literal: true
+
+require "exceptions"
+require "hardware"
+require "version"
+
+module OS
+  module Mac
+    # A macOS version.
+    #
+    # @api private
+    class Version < ::Version
+      extend T::Sig
+
+      # TODO: bump version when new macOS is released or announced
+      # and also update references in docs/Installation.md,
+      # https://github.com/Homebrew/install/blob/HEAD/install.sh and
+      # MacOSVersions::SYMBOLS
+      NEWEST_UNSUPPORTED = "14"
+      private_constant :NEWEST_UNSUPPORTED
+
+      # TODO: bump version when new macOS is released and also update
+      # references in docs/Installation.md and
+      # https://github.com/Homebrew/install/blob/HEAD/install.sh
+      OLDEST_SUPPORTED = "10.15"
+      private_constant :OLDEST_SUPPORTED
+
+      OLDEST_ALLOWED = "10.11"
+
+      sig { params(version: Symbol).returns(T.attached_class) }
+      def self.from_symbol(version)
+        str = MacOSVersions::SYMBOLS.fetch(version) { raise MacOSVersionError, version }
+        new(str)
+      end
+
+      sig { params(value: T.nilable(String)).void }
+      def initialize(value)
+        version ||= value
+
+        raise MacOSVersionError, version unless /\A1\d+(?:\.\d+){0,2}\Z/.match?(version)
+
+        super(version)
+
+        @comparison_cache = {}
+      end
+
+      sig { override.params(other: T.untyped).returns(T.nilable(Integer)) }
+      def <=>(other)
+        @comparison_cache.fetch(other) do
+          if MacOSVersions::SYMBOLS.key?(other) && to_sym == other
+            0
+          else
+            v = MacOSVersions::SYMBOLS.fetch(other) { other.to_s }
+            @comparison_cache[other] = super(::Version.new(v))
+          end
+        end
+      end
+
+      sig { returns(T.self_type) }
+      def strip_patch
+        # Big Sur is 11.x but Catalina is 10.15.x.
+        if major >= 11
+          self.class.new(major.to_s)
+        else
+          major_minor
+        end
+      end
+
+      sig { returns(Symbol) }
+      def to_sym
+        @to_sym ||= MacOSVersions::SYMBOLS.invert.fetch(strip_patch.to_s, :dunno)
+      end
+
+      sig { returns(String) }
+      def pretty_name
+        @pretty_name ||= to_sym.to_s.split("_").map(&:capitalize).join(" ").freeze
+      end
+
+      sig { returns(T::Boolean) }
+      def outdated_release?
+        self < OLDEST_SUPPORTED
+      end
+
+      sig { returns(T::Boolean) }
+      def prerelease?
+        self >= NEWEST_UNSUPPORTED
+      end
+
+      # For {OS::Mac::Version} compatibility.
+      sig { returns(T::Boolean) }
+      def requires_nehalem_cpu?
+        unless Hardware::CPU.intel?
+          raise "Unexpected architecture: #{Hardware::CPU.arch}. This only works with Intel architecture."
+        end
+
+        Hardware.oldest_cpu(self) == :nehalem
+      end
+      # https://en.wikipedia.org/wiki/Nehalem_(microarchitecture)
+      # Ensure any extra methods are also added to version/null.rb
+      alias requires_sse4? requires_nehalem_cpu?
+      alias requires_sse41? requires_nehalem_cpu?
+      alias requires_sse42? requires_nehalem_cpu?
+      alias requires_popcnt? requires_nehalem_cpu?
+    end
+  end
+end

docs/Installation.md

@@ -9,7 +9,7 @@ The macOS `.pkg` installer also installs Homebrew to its default prefix (`/opt/h
 ## macOS Requirements
 
 * A 64-bit Intel CPU or Apple Silicon CPU <sup>[1](#1)</sup>
-* macOS Big Sur (11) (or higher) <sup>[2](#2)</sup>
+* macOS Catalina (10.5) (or higher) <sup>[2](#2)</sup>
 * Command Line Tools (CLT) for Xcode (from `xcode-select --install` or
   [https://developer.apple.com/download/all/](https://developer.apple.com/download/all/)) or
   [Xcode](https://itunes.apple.com/us/app/xcode/id497799835) <sup>[3](#3)</sup>
@@ -90,7 +90,7 @@ Uninstallation is documented in the [FAQ](FAQ.md).
 
 <a name="1"><sup>1</sup></a> For 32-bit or PPC support see [Tigerbrew](https://github.com/mistydemeo/tigerbrew).
 
-<a name="2"><sup>2</sup></a> macOS 11 (Big Sur) or higher is best and supported, 10.11 (El Capitan) – 10.15 (Catalina) are unsupported but may work and 10.10 (Yosemite) and older will not run Homebrew at all. For 10.4 (Tiger) – 10.6 (Snow Leopard) see [Tigerbrew](https://github.com/mistydemeo/tigerbrew).
+<a name="2"><sup>2</sup></a> macOS 10.5 (Catalina) or higher is best and supported, 10.11 (El Capitan) – 10.15 (Catalina) are unsupported but may work and 10.10 (Yosemite) and older will not run Homebrew at all. For 10.4 (Tiger) – 10.6 (Snow Leopard) see [Tigerbrew](https://github.com/mistydemeo/tigerbrew).
 
 <a name="3"><sup>3</sup></a> You may need to install Xcode, the CLT, or both depending on the formula, to install a bottle (binary package) which is the only supported configuration. Downloading Xcode may require an Apple Developer account on older versions of Mac OS X. Sign up for free at [Apple's website](https://developer.apple.com/account/).