git: install OS X keychain credential helper

Git can cache credentials used when accessing remotes over HTTP; this
helper provides integration with the OS X keychain.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

Library/Formula/git.rb

@@ -52,6 +52,13 @@ def install
                    "LDFLAGS=#{ENV.ldflags}",
                    "install"
 
+    # Install the OS X keychain credential helper
+    cd 'contrib/credential/osxkeychain' do
+      system "make", "CC=#{ENV.cc}", "CFLAGS=#{ENV.cflags}"
+      bin.install 'git-credential-osxkeychain'
+      system "make", "clean"
+    end
+
     # install the completion script first because it is inside 'contrib'
     (prefix+'etc/bash_completion.d').install 'contrib/completion/git-completion.bash'
     (share+'git-core').install 'contrib'
@@ -66,6 +73,9 @@ def caveats; <<-EOS.undent
     Bash completion has been installed to:
       #{etc}/bash_completion.d
 
+    The OS X keychain credential helper has been installed to:
+      #{HOMEBREW_PREFIX}/bin/git-credential-osxkeychain
+
     The 'contrib' directory has been installed to:
       #{HOMEBREW_PREFIX}/share/git-core/contrib
     EOS