rustc-completion: import from homebrew/completions.

Formula/rustc-completion.rb

@@ -0,0 +1,28 @@
+class RustcCompletion < Formula
+  desc "Bash completion for rustc"
+  homepage "https://github.com/roshan/rust-bash-completion"
+
+  head "https://github.com/roshan/rust-bash-completion.git"
+
+  stable do
+    url "https://github.com/roshan/rust-bash-completion/archive/0.12.1.tar.gz"
+    sha256 "562f84ccab40f2b3e7ef47e2e6d9b6615070a0e7330d64ea5368b6ad75455012"
+
+    # upstream commit to fix an undefined command when sourcing the file directly
+    patch do
+      url "https://github.com/roshan/rust-bash-completion/commit/932e9bb4e9f28c2785de2b8db6f0e8c050f4f9be.diff"
+      sha256 "0d5f4762bd93ffe09ee86c6ffffc850337ee69a8a54049c8b29a113468b39618"
+    end
+  end
+
+  bottle :unneeded
+
+  def install
+    bash_completion.install "etc/bash_completion.d/rustc"
+  end
+
+  test do
+    assert_match "-F _rustc",
+      shell_output("source #{bash_completion}/rustc && complete -p rustc")
+  end
+end