From 09a9d216d926a77c8152bf8cccd880e133c41256 Mon Sep 17 00:00:00 2001
From: "Stefan J. Wernli" <swernli@microsoft.com>
Date: Fri, 25 Sep 2015 14:00:56 -0700
Subject: [PATCH] Windows: Fixing longpath hanlding of UNC paths.

Signed-off-by: Stefan J. Wernli <swernli@microsoft.com>
---
 longpath/longpath.go      |  7 ++++++-
 longpath/longpath_test.go | 22 ++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)
 create mode 100644 longpath/longpath_test.go

diff --git a/longpath/longpath.go b/longpath/longpath.go
index 1dcc10a..9b15bff 100644
--- a/longpath/longpath.go
+++ b/longpath/longpath.go
@@ -15,7 +15,12 @@ const Prefix = `\\?\`
 // it does not already have it.
 func AddPrefix(path string) string {
 	if !strings.HasPrefix(path, Prefix) {
-		path = Prefix + path
+		if strings.HasPrefix(path, `\\`) {
+			// This is a UNC path, so we need to add 'UNC' to the path as well.
+			path = Prefix + `UNC` + path[1:]
+		} else {
+			path = Prefix + path
+		}
 	}
 	return path
 }
diff --git a/longpath/longpath_test.go b/longpath/longpath_test.go
new file mode 100644
index 0000000..01865ef
--- /dev/null
+++ b/longpath/longpath_test.go
@@ -0,0 +1,22 @@
+package longpath
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestStandardLongPath(t *testing.T) {
+	c := `C:\simple\path`
+	longC := AddPrefix(c)
+	if !strings.EqualFold(longC, `\\?\C:\simple\path`) {
+		t.Errorf("Wrong long path returned. Original = %s ; Long = %s", c, longC)
+	}
+}
+
+func TestUNCLongPath(t *testing.T) {
+	c := `\\server\share\path`
+	longC := AddPrefix(c)
+	if !strings.EqualFold(longC, `\\?\UNC\server\share\path`) {
+		t.Errorf("Wrong UNC long path returned. Original = %s ; Long = %s", c, longC)
+	}
+}