tree: fix colored output on windows

Since rclone version 1.61.0 the tree command uses ANSI color sequences in output by
default, but this lead to issues in Windows terminals that were not handling these (#6668).

This commit ensures the tree command uses the terminal package for output. It relies on
go-colorable to properly handle ANSI color sequences: If stdout is connected to a terminal
the escape sequences are decoded and the text are written with color formatting using
Windows Console API. If stdout is not connected to a terminal, e.g. redirected to file,
the escape sequences are stripped off. The tree command has its own method for writing
directly to a file, specified with flag --output, and then the output is not passed
through the terminal package and must therefore be written without ansi codes.

cmd/tree/tree.go

@@ -18,6 +18,7 @@ import (
 	"github.com/rclone/rclone/fs/dirtree"
 	"github.com/rclone/rclone/fs/log"
 	"github.com/rclone/rclone/fs/walk"
+	"github.com/rclone/rclone/lib/terminal"
 	"github.com/spf13/cobra"
 )
 
@@ -100,22 +101,26 @@ For a more interactive navigation of the remote see the
 	RunE: func(command *cobra.Command, args []string) error {
 		cmd.CheckArgs(1, 1, command, args)
 		fsrc := cmd.NewFsSrc(args)
-		outFile := os.Stdout
+		ci := fs.GetConfig(context.Background())
+		var outFile io.Writer
 		if outFileName != "" {
 			var err error
 			outFile, err = os.Create(outFileName)
 			if err != nil {
 				return fmt.Errorf("failed to create output file: %w", err)
 			}
+			opts.Colorize = false
+		} else {
+			terminal.Start()
+			outFile = terminal.Out
+			opts.Colorize = true
 		}
 		opts.VerSort = opts.VerSort || sort == "version"
 		opts.ModSort = opts.ModSort || sort == "mtime"
 		opts.CTimeSort = opts.CTimeSort || sort == "ctime"
 		opts.NameSort = sort == "name"
 		opts.SizeSort = sort == "size"
-		ci := fs.GetConfig(context.Background())
 		opts.UnitSize = ci.HumanReadable
-		opts.Colorize = ci.TerminalColorMode != fs.TerminalColorModeNever
 		if opts.DeepLevel == 0 {
 			opts.DeepLevel = ci.MaxDepth
 		}