repo: Upgrade: use branch or commit

Author: jrotkiewicz

newt/repo/repo.go

@@ -318,13 +318,19 @@ func (r *Repo) DirtyState() (string, error) {
 }
 
 func (r *Repo) Upgrade(ver newtutil.RepoVersion) error {
-	commit, err := r.CommitFromVer(ver)
-	if err != nil {
-		return err
-	}
+	if branch := r.downloader.MainBranch(); branch != "" {
+		if err := r.updateRepo(branch); err != nil {
+			return err
+		}
+	} else {
+		commit, err := r.CommitFromVer(ver)
+		if err != nil {
+			return err
+		}
 
-	if err := r.updateRepo(commit); err != nil {
-		return err
+		if err := r.updateRepo(commit); err != nil {
+			return err
+		}
 	}
 
 	return nil