net/url: strip relative path components for JoinPath

Signed-off-by: cui fliter <[email protected]>

Author: cuishuang

src/net/url/url.go

@@ -1197,6 +1197,10 @@ func (u *URL) JoinPath(elem ...string) *URL {
 	url := *u
 	if len(elem) > 0 {
 		elem = append([]string{u.EscapedPath()}, elem...)
+		// fix issue https://golang.org/issue/54385
+		if elem[0] == "" && strings.HasPrefix(elem[1], "../") {
+			elem[0] = "/"
+		}
 		p := path.Join(elem...)
 		// path.Join will remove any trailing slashes.
 		// Preserve at least one.

src/net/url/url_test.go

@@ -2090,6 +2090,11 @@ func TestJoinPath(t *testing.T) {
 			elem: []string{"/go"},
 			out:  "https://go.googlesource.com/go",
 		},
+		{
+			base: "https://go.googlesource.com",
+			elem: []string{"../go"},
+			out:  "https://go.googlesource.com/go",
+		},
 		{
 			base: "https://go.googlesource.com//",
 			elem: []string{"/go", "a", "b", "c"},