Clean and simplify vendor.sh while making it easier to maintain as well

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)

hack/vendor.sh

@@ -1,54 +1,52 @@
 #!/bin/bash
+set -e
 
-# Downloads dependencies into vendor/ directory
-if [[ ! -d vendor ]]; then
-  mkdir vendor
-fi
-vendor_dir=${PWD}/vendor
-
-rm_pkg_dir () {
-  PKG=$1
-  REV=$2
-  (
-    set -e
-    cd $vendor_dir
-    if [[ -d src/$PKG ]]; then
-      echo "src/$PKG already exists. Removing."
-      rm -fr src/$PKG
-    fi
-  )
-}
+cd "$(dirname "$BASH_SOURCE")/.."
 
-git_clone () {
-  PKG=$1
-  REV=$2
-  (
-    set -e
-    rm_pkg_dir $PKG $REV
-    cd $vendor_dir && git clone http://$PKG src/$PKG
-    cd src/$PKG && git checkout -f $REV && rm -fr .git
-  )
-}
-
-hg_clone () {
-  PKG=$1
-  REV=$2
-  (
-    set -e
-    rm_pkg_dir $PKG $REV
-    cd $vendor_dir && hg clone http://$PKG src/$PKG
-    cd src/$PKG && hg checkout -r $REV && rm -fr .hg
-  )
+# Downloads dependencies into vendor/ directory
+mkdir -p vendor
+cd vendor
+
+clone() {
+	vcs=$1
+	pkg=$2
+	rev=$3
+	
+	pkg_url=https://$pkg
+	target_dir=src/$pkg
+	
+	echo -n "$pkg @ $rev: "
+	
+	if [ -d $target_dir ]; then
+		echo -n 'rm old, '
+		rm -fr $target_dir
+	fi
+	
+	echo -n 'clone, '
+	case $vcs in
+		git)
+			git clone --quiet --no-checkout $pkg_url $target_dir
+			( cd $target_dir && git reset --quiet --hard $rev )
+			;;
+		hg)
+			hg clone --quiet --updaterev $rev $pkg_url $target_dir
+			;;
+	esac
+	
+	echo -n 'rm VCS, '
+	( cd $target_dir && rm -rf .{git,hg} )
+	
+	echo done
 }
 
-git_clone github.com/kr/pty 3b1f6487b
+clone git github.com/kr/pty 3b1f6487b
 
-git_clone github.com/gorilla/context/ 708054d61e5
+clone git github.com/gorilla/context 708054d61e5
 
-git_clone github.com/gorilla/mux/ 9b36453141c
+clone git github.com/gorilla/mux 9b36453141c
 
-git_clone github.com/syndtr/gocapability 3454319be2
+clone git github.com/syndtr/gocapability 3454319be2
 
-hg_clone code.google.com/p/go.net 84a4013f96e0
+clone hg code.google.com/p/go.net 84a4013f96e0
 
-hg_clone code.google.com/p/gosqlite 74691fb6f837
+clone hg code.google.com/p/gosqlite 74691fb6f837