Add Homebrew formula reference and installation docs

docs/GettingGrate.md

@@ -64,7 +64,13 @@ grate is available on [winget](https://docs.microsoft.com/en-us/windows/package-
 
 ## Homebrew
 
-grate is available as a Homebrew cask. Simply `brew install --cask erikbra/cask/grate` for awesomeness!
+grate is available as a Homebrew formula:
+
+```sh
+brew install grate
+```
+
+The formula installs a self-contained binary, so the .NET runtime is not required on the target computer.
 
 ## Notes
 

installers/homebrew/grate.rb

@@ -0,0 +1,66 @@
+class Grate < Formula
+  desc "SQL migration tool using plain SQL scripts"
+  homepage "https://grate-devs.github.io/grate/"
+  url "https://github.com/grate-devs/grate/archive/refs/tags/2.1.6.tar.gz"
+  sha256 "456d83d3ce605720241fd32b386c2a2f9f1adefaa11af77bfcbcb0bd5e1090b5"
+  license "MIT"
+  head "https://github.com/grate-devs/grate.git", branch: "main"
+
+  depends_on "dotnet" => :build
+  depends_on "brotli"
+
+  on_linux do
+    depends_on "icu4c@78"
+    depends_on "libunwind"
+    depends_on "zlib-ng-compat"
+  end
+
+  def install
+    ENV["DOTNET_CLI_TELEMETRY_OPTOUT"] = "1"
+    ENV["DOTNET_NOLOGO"] = "1"
+
+    # Use Homebrew's supported SDK rather than the feature band pinned upstream.
+    rm "global.json"
+
+    dotnet = Formula["dotnet"]
+    framework = "net#{dotnet.version.major_minor}"
+    args = %W[
+      --configuration Release
+      --framework #{framework}
+      --output #{libexec}
+      --self-contained
+      --use-current-runtime
+      -p:DebugType=None
+      -p:IncludeNativeLibrariesForSelfExtract=true
+      -p:PublishSingleFile=true
+      -p:TargetFrameworks=#{framework}
+    ]
+    args << "-p:Version=#{version}" if build.stable?
+
+    system "dotnet", "publish", "src/grate/grate.csproj", *args
+    bin.install libexec/"grate"
+  end
+
+  test do
+    scripts = testpath/"scripts"/"up"
+    scripts.mkpath
+    (scripts/"001_create_widgets.sql").write <<~SQL
+      CREATE TABLE widgets (
+        id INTEGER PRIMARY KEY,
+        name TEXT NOT NULL
+      );
+    SQL
+
+    database = testpath/"grate-test.db"
+    system bin/"grate",
+           "--connectionstring", "Data Source=#{database}",
+           "--databasetype", "sqlite",
+           "--sqlfilesdirectory", testpath/"scripts",
+           "--output", testpath/"output",
+           "--version", version.to_s,
+           "--silent"
+
+    assert_path_exists database
+    assert_predicate database, :size?
+  end
+end