client: use canonical url path in request

The main change is that it keeps the trailing slash. This helps
auth feature to judge path permission accurately.

pkg/pathutil/path.go

@@ -0,0 +1,38 @@
+// Copyright 2015 CoreOS, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package pathutil
+
+import "path"
+
+// CanonicalURLPath returns the canonical url path for p, which follows the rules:
+// 1. the path always starts with "/"
+// 2. replace multiple slashes with a single slash
+// 3. replace each '.' '..' path name element with equivalent one
+// 4. keep the trailing slash
+func CanonicalURLPath(p string) string {
+	if p == "" {
+		return "/"
+	}
+	if p[0] != '/' {
+		p = "/" + p
+	}
+	np := path.Clean(p)
+	// path.Clean removes trailing slash except for root,
+	// put the trailing slash back if necessary.
+	if p[len(p)-1] == '/' && np != "/" {
+		np += "/"
+	}
+	return np
+}