switch to go vendoring

vendor/github.com/huandu/xstrings/common.go

@@ -0,0 +1,21 @@
+// Copyright 2015 Huan Du. All rights reserved.
+// Licensed under the MIT license that can be found in the LICENSE file.
+
+package xstrings
+
+const bufferMaxInitGrowSize = 2048
+
+// Lazy initialize a buffer.
+func allocBuffer(orig, cur string) *stringBuilder {
+	output := &stringBuilder{}
+	maxSize := len(orig) * 4
+
+	// Avoid to reserve too much memory at once.
+	if maxSize > bufferMaxInitGrowSize {
+		maxSize = bufferMaxInitGrowSize
+	}
+
+	output.Grow(maxSize)
+	output.WriteString(orig[:len(orig)-len(cur)])
+	return output
+}