Change most global flags into local ones

This is to ensure that only the relevant command-line flags
for a certain Hugo subcommand is shown to the end user,
reducing clutter and improving user experience.

Fixes #1624 - CLI UX: Flags shouldn't be global

commands/list.go

@@ -25,6 +25,7 @@ import (
 func init() {
 	listCmd.AddCommand(listDraftsCmd)
 	listCmd.AddCommand(listFutureCmd)
+	listCmd.PersistentFlags().StringVarP(&Source, "source", "s", "", "filesystem path to read files relative from")
 }
 
 var listCmd = &cobra.Command{