Add Homebrew formula.

The build-setup is pinched from [gitsh]. Thanks @georgebrock and
@mike-burns.

Closes #27.

[gitsh]: https://github.com/thoughtbot/gitsh/

.gitignore

@@ -2,6 +2,7 @@
 core*
 pick
 vgcore*
+homebrew-formulae
 
 # Generated by Autotools
 .deps

DEVELOPING.md

@@ -51,3 +51,7 @@ Release
 
 6. [Announce the release on
    GitHub](https://github.com/thoughtbot/pick/releases/new).
+
+7. Release Homebrew package by running:
+
+        make release

Makefile.am

@@ -4,3 +4,40 @@ EXTRA_DIST=INSTALL.md INSTALL.md.in LICENSE README.md
 
 INSTALL.md: INSTALL.md.in
 	sed -e 's|@PACKAGE_VERSION[@]|$(PACKAGE_VERSION)|g' $@.in > $@
+
+.PHONY: release \
+	release_build release_push release_clean \
+	release_build_homebrew \
+	release_push_homebrew \
+	release_clean_homebrew
+
+edit_package = sed \
+	-e 's|@PACKAGE[@]|$(PACKAGE)|g' \
+	-e 's|@PACKAGE_VERSION[@]|$(PACKAGE_VERSION)|g' \
+	-e 's|@DIST_ARCHIVES[@]|$(DIST_ARCHIVES)|g' \
+	-e 's|@DIST_SHA[@]|$(DIST_SHA)|g'
+
+release: release_build release_push release_clean
+
+release_build: release_build_homebrew
+
+release_push: release_push_homebrew
+
+release_clean: release_clean_homebrew
+
+release_build_homebrew: DIST_SHA
+	git clone git@github.com:thoughtbot/homebrew-formulae.git homebrew-formulae
+	$(edit_package) homebrew/pick.rb.in > homebrew-formulae/Formula/pick.rb
+	cd homebrew-formulae &&\
+		git addd Formula/pick.rb &&\
+		git commit -am "pick: Release version $(PACKAGE_VERSION)"
+
+release_push_homebrew:
+	cd homebrew-formulae &&\
+		git push
+
+release_clean_homebrew:
+	rm -rf homebrew-formulae
+
+DIST_SHA: Makefile distcheck
+	$(eval DIST_SHA := $(shell shasum $(srcdir)/$(DIST_ARCHIVES) | cut -d' ' -f1))

homebrew/pick.rb.in

@@ -0,0 +1,16 @@
+require "formula"
+
+class Pick < Formula
+  homepage "http://thoughtbot.github.io/@PACKAGE@/"
+  url "https://github.com/thoughtbot/@PACKAGE@/releases/download/v@PACKAGE_VERSION@/@DIST_ARCHIVES@"
+  sha1 "@DIST_SHA@"
+
+  def install
+    system "./configure", "--prefix=#{prefix}"
+    system "make", "install"
+  end
+
+  test do
+    system "#{bin}/pick", "-v"
+  end
+end