add check if repo exists

operations/fetch.go

@@ -248,6 +248,17 @@ type cloneOptions struct {
 }
 
 func clone(opts cloneOptions) error {
+	// Check repository existence if no token is provided
+	if opts.token == "" {
+		resp, err := http.Get(thirdparty.FormGitURLForApp("github.com", opts.owner, opts.repository, opts.token))
+		if err != nil {
+			return errors.Errorf("failed to check if %s/%s exists: %v", opts.owner, opts.repository, err)
+		}
+		defer resp.Body.Close()
+		if resp.StatusCode != http.StatusOK {
+			return errors.Errorf("repository does not exist or is private an no token was provided: %d", resp.StatusCode)
+		}
+	}
 	var cloneArgs []string
 	// clone the repo first
 	if opts.isAppToken {