misc/makerelease: handle git sub-repositories

Also: checkout sub-repos from Mercurial manually
instead of using "go get". (for the 1.4 release)

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/190720043

misc/makerelease/makerelease.go

@@ -505,15 +505,31 @@ func (b *Build) extras() error {
 }
 
 func (b *Build) get(repoPath, revision string) error {
-	// Fetch the packages (without building/installing).
-	_, err := b.run(b.gopath, filepath.Join(b.root, "bin", "go"),
-		"get", "-d", repoPath+"/...")
-	if err != nil {
-		return err
+	dest := filepath.Join(b.gopath, "src", filepath.FromSlash(repoPath))
+
+	if strings.HasPrefix(repoPath, "golang.org/x/") {
+		// For sub-repos, fetch the old Mercurial repo; bypass "go get".
+		// DO NOT import this special case into the git tree.
+
+		if err := os.MkdirAll(filepath.Dir(dest), 0755); err != nil {
+			return err
+		}
+		repo := strings.Replace(repoPath, "golang.org/x/", "https://code.google.com/p/go.", 1)
+		if _, err := b.run(b.gopath, "hg", "clone", repo, dest); err != nil {
+			return err
+		}
+	} else {
+		// Fetch the packages (without building/installing).
+		_, err := b.run(b.gopath, filepath.Join(b.root, "bin", "go"),
+			"get", "-d", repoPath+"/...")
+		if err != nil {
+			return err
+		}
 	}
 
 	// Update the repo to the specified revision.
 	dest := filepath.Join(b.gopath, "src", filepath.FromSlash(repoPath))
+	var err error
 	switch {
 	case exists(filepath.Join(dest, ".git")):
 		_, err = b.run(dest, "git", "checkout", revision)