goinstall: use correct checkout URL for Google Code svn repos

Fixes #2655.

R=golang-dev, gri
CC=golang-dev
https://golang.org/cl/5510045

src/cmd/goinstall/download.go

@@ -236,9 +236,13 @@ func (r *googleRepo) Repo(client *http.Client) (url, root string, vcs *vcs, err
 	}
 
 	// Scrape result for vcs details.
-	m := googleRepoRe.FindSubmatch(b)
-	if len(m) == 2 {
-		if v := vcsMap[string(m[1])]; v != nil {
+	if m := googleRepoRe.FindSubmatch(b); len(m) == 2 {
+		s := string(m[1])
+		if v := vcsMap[s]; v != nil {
+			if s == "svn" {
+				// Subversion still uses the old-style URL.
+				r.url = fmt.Sprintf("http://%s.googlecode.com/svn", p[0])
+			}
 			r.vcs = v
 			return r.url, r.root, r.vcs, nil
 		}

src/cmd/goinstall/download_test.go

@@ -31,7 +31,7 @@ var FindPublicRepoTests = []struct {
 		"code.google.com/p/repo/path/foo",
 		"svn",
 		"code.google.com/p/repo",
-		"https://code.google.com/p/repo",
+		"https://repo.googlecode.com/svn",
 		&testTransport{
 			"https://code.google.com/p/repo/source/checkout",
 			`<tt id="checkoutcmd">svn checkout https://...`,