refactor: simplify config into a single load/save with defaults resolved at load time

src/cmd/edit.go

@@ -33,7 +33,7 @@ var editCmd = &cobra.Command{
 		tmp.Close()
 		defer os.Remove(tmp.Name())
 
-		c := exec.Command(cfg.GetEditor(), tmp.Name())
+		c := exec.Command(cfg.Editor, tmp.Name())
 		c.Stdin, c.Stdout, c.Stderr = os.Stdin, os.Stdout, os.Stderr
 		if err := c.Run(); err != nil {
 			fmt.Fprintln(os.Stderr, "editor failed:", err)