From ee163197a879cf19aa9758bc544c717445284311 Mon Sep 17 00:00:00 2001
From: Federico Guerinoni <guerinoni.federico@gmail.com>
Date: Tue, 7 Oct 2025 01:13:14 +0200
Subject: [PATCH] path/filepath: return cleaned path from Rel

As the doc says, Rel should return a cleaned path.

Fixes #75763

Change-Id: Ic0f5a3b1da3cc4cf3c31fdb1a88ebcc4ea6f9169
Reviewed-on: https://go-review.googlesource.com/c/go/+/709675
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Sean Liao <sean@liao.dev>
Auto-Submit: Sean Liao <sean@liao.dev>
Reviewed-by: Carlos Amedee <carlos@golang.org>
---
 src/path/filepath/path.go      | 2 +-
 src/path/filepath/path_test.go | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/path/filepath/path.go b/src/path/filepath/path.go
index 5ffd9f0b6c..dc6975242a 100644
--- a/src/path/filepath/path.go
+++ b/src/path/filepath/path.go
@@ -248,7 +248,7 @@ func Rel(basepath, targpath string) (string, error) {
 			buf[n] = Separator
 			copy(buf[n+1:], targ[t0:])
 		}
-		return string(buf), nil
+		return Clean(string(buf)), nil
 	}
 	return targ[t0:], nil
 }
diff --git a/src/path/filepath/path_test.go b/src/path/filepath/path_test.go
index 7ea02a7c28..efdb3c6035 100644
--- a/src/path/filepath/path_test.go
+++ b/src/path/filepath/path_test.go
@@ -1506,6 +1506,7 @@ var reltests = []RelTests{
 	{"/../../a/b", "/../../a/b/c/d", "c/d"},
 	{".", "a/b", "a/b"},
 	{".", "..", ".."},
+	{"", "../../.", "../.."},
 
 	// can't do purely lexically
 	{"..", ".", "err"},
-- 
2.52.0