Using git commit sha in tests

[sameersbn]

I am writing a formula (snippet below) which builds the package from a git repo. The version sub command of the tool returns the sha of the git commit in it's output. In my tests, I want to check if the sha matches the one as specified in the formula (the revision field). Is there a variable available which makes the git revision available for use in the tests?

Thanks in advance.

class Kn < Formula
  desc "Command-line interface for managing Knative Serving and Eventing resources"
  homepage "https://github.com/knative/client"
  url "https://github.com/knative/client.git",
      tag:      "v0.24.0",
      revision: "0bbb3ec9d92665d372d8393ef3036ba7e0c069a4"
  license "Apache-2.0"

  depends_on "bash" => :build
  depends_on "go" => :build

  def install
    ENV["CGO_ENABLED"] = "0"
    ENV["GO111MODULE"] = "on"
    ENV["TAG"]         = "v#{version}"

    system "./hack/build.sh", "--fast"

    bin.install "kn"
  end

  test do
    version_output = shell_output("#{bin}/kn version")
    assert_match("Version:      v#{version}", version_output)
    assert_match("Git Revision: ", version_output)
  end
end

in assert_match("Git Revision: ", version_output) i want to do something like assert_match("Git Revision: #{revision}", version_output)