backup: Reenable JSON status updates with redirected output

After the refactoring status updates were no longer printed in quiet
mode or when the output is not an interactive terminal. However, the
JSON output is often piped to e.g. another program. Thus, don't set the
update frequency to 0 in that case. The status updates are still
disabled for backup --quiet.

This also reduces the status update frequency to 60fps compared to a
potentially much higher value before the refactoring.

cmd/restic/cmd_backup.go

@@ -547,7 +547,7 @@ func runBackup(opts BackupOptions, gopts GlobalOptions, term *termstatus.Termina
 	}()
 	gopts.stdout, gopts.stderr = progressPrinter.Stdout(), progressPrinter.Stderr()
 
-	progressReporter.SetMinUpdatePause(calculateProgressInterval(!gopts.Quiet))
+	progressReporter.SetMinUpdatePause(calculateProgressInterval(!gopts.Quiet, gopts.JSON))
 
 	t.Go(func() error { return progressReporter.Run(t.Context(gopts.ctx)) })
 

cmd/restic/progress.go

@@ -14,7 +14,7 @@ import (
 // calculateProgressInterval returns the interval configured via RESTIC_PROGRESS_FPS
 // or if unset returns an interval for 60fps on interactive terminals and 0 (=disabled)
 // for non-interactive terminals or when run using the --quiet flag
-func calculateProgressInterval(show bool) time.Duration {
+func calculateProgressInterval(show bool, json bool) time.Duration {
 	interval := time.Second / 60
 	fps, err := strconv.ParseFloat(os.Getenv("RESTIC_PROGRESS_FPS"), 64)
 	if err == nil && fps > 0 {
@@ -22,7 +22,7 @@ func calculateProgressInterval(show bool) time.Duration {
 			fps = 60
 		}
 		interval = time.Duration(float64(time.Second) / fps)
-	} else if !stdoutCanUpdateStatus() || !show {
+	} else if !json && !stdoutCanUpdateStatus() || !show {
 		interval = 0
 	}
 	return interval
@@ -33,7 +33,7 @@ func newProgressMax(show bool, max uint64, description string) *progress.Counter
 	if !show {
 		return nil
 	}
-	interval := calculateProgressInterval(show)
+	interval := calculateProgressInterval(show, false)
 	canUpdateStatus := stdoutCanUpdateStatus()
 
 	return progress.New(interval, max, func(v uint64, max uint64, d time.Duration, final bool) {