net/http: escape path in implicit /tree→/tree/ ServeMux.Handle redirect

Fixes #10572

Change-Id: I764f3c226cf98ff39d9e553e4613d0ee108ef766
Reviewed-on: https://go-review.googlesource.com/9311Reviewed-by: Russ Cox <rsc@golang.org>

src/net/http/serve_test.go

@@ -207,6 +207,7 @@ var handlers = []struct {
 }{
 	{"/", "Default"},
 	{"/someDir/", "someDir"},
+	{"/#/", "hash"},
 	{"someHost.com/someDir/", "someHost.com/someDir"},
 }
 
@@ -215,12 +216,14 @@ var vtests = []struct {
 	expected string
 }{
 	{"http://localhost/someDir/apage", "someDir"},
+	{"http://localhost/%23/apage", "hash"},
 	{"http://localhost/otherDir/apage", "Default"},
 	{"http://someHost.com/someDir/apage", "someHost.com/someDir"},
 	{"http://otherHost.com/someDir/apage", "someDir"},
 	{"http://otherHost.com/aDir/apage", "Default"},
 	// redirections for trees
 	{"http://localhost/someDir", "/someDir/"},
+	{"http://localhost/%23", "/%23/"},
 	{"http://someHost.com/someDir", "/someDir/"},
 }
 

src/net/http/server.go

@@ -1667,7 +1667,8 @@ func (mux *ServeMux) Handle(pattern string, handler Handler) {
 			// strings.Index can't be -1.
 			path = pattern[strings.Index(pattern, "/"):]
 		}
-		mux.m[pattern[0:n-1]] = muxEntry{h: RedirectHandler(path, StatusMovedPermanently), pattern: pattern}
+		url := &url.URL{Path: path}
+		mux.m[pattern[0:n-1]] = muxEntry{h: RedirectHandler(url.String(), StatusMovedPermanently), pattern: pattern}
 	}
 }