vendor.sh can cleanly update vendored dependencies

hack/vendor.sh

@@ -0,0 +1,39 @@
+#!/bin/bash
+
+# Downloads dependencies into vendor/ directory
+if [[ ! -d vendor ]]; then
+  mkdir vendor
+fi
+vendor_dir=${PWD}/vendor
+
+git_clone () {
+  PKG=$1
+  REV=$2
+  (
+    set -e
+    cd $vendor_dir
+    if [[ ! -d src/$PKG ]]; then
+      cd $vendor_dir && git clone http://$PKG src/$PKG
+    fi
+    cd src/$PKG && git checkout -f $REV
+  )
+}
+
+git_clone github.com/kr/pty 27435c699
+
+git_clone github.com/gorilla/context/ 708054d61e5
+
+git_clone github.com/gorilla/mux/ 9b36453141c
+
+git_clone github.com/dotcloud/tar/ d06045a6d9
+
+# Docker requires code.google.com/p/go.net/websocket
+PKG=code.google.com/p/go.net REV=84a4013f96e0
+(
+  set -e
+  cd $vendor_dir
+  if [[ ! -d src/$PKG ]]; then
+    hg clone https://$PKG src/$PKG
+  fi
+  cd src/$PKG && hg checkout -r $REV
+)