improve conflict error messages, add -v to usage

main.go

@@ -56,6 +56,7 @@ func usage() {
 	fmt.Println("  sigil unlink <package> [--dry-run]")
 	fmt.Println("  sigil remove <package> [--dry-run]")
 	fmt.Println("  sigil status")
+	fmt.Println("  sigil -v, --version")
 }
 
 func applyCmd(args []string) error {

ops.go

@@ -63,9 +63,9 @@ func linkFile(src, dst string) error {
 			if current == src {
 				return nil
 			}
-			return fmt.Errorf("conflict at %s (points to %s)", dst, current)
+			return fmt.Errorf("conflict at %s (symlink points to %s, expected %s). Run 'sigil unlink %s' to restore and remove the conflicting link", dst, current, src, dst)
 		}
-		return fmt.Errorf("conflict at %s (exists and is not a symlink)", dst)
+		return fmt.Errorf("conflict at %s (file exists and is not a symlink). Back up or remove this file first", dst)
 	} else if !errors.Is(err, os.ErrNotExist) {
 		return err
 	}