ui: update status for the backup command on non-interactive terminals

Allow the backup command to print status on non-interactive terminals.
The output is disabled by setting a MinUpdatePause == 0.

doc/manual_rest.rst

@@ -135,10 +135,10 @@ command:
 
 Subcommands that support showing progress information such as ``backup``,
 ``check`` and ``prune`` will do so unless the quiet flag ``-q`` or
-``--quiet`` is set. For interactive consoles the environment variable
+``--quiet`` is set. When running from a non-interactive console progress
-``RESTIC_PROGRESS_FPS`` can be used to control the frequency of progress
+reporting is disabled by default to not fill your logs. For interactive
-reporting. When running from a non-interactive console progress reporting
+and non-interactive consoles the environment variable ``RESTIC_PROGRESS_FPS``
-is disabled to not fill your logs.
+can be used to control the frequency of progress reporting.
 
 Additionally, on Unix systems if ``restic`` receives a SIGUSR1 signal the
 current progress will be written to the standard output so you can check up

internal/ui/backup.go

@@ -90,7 +90,11 @@ func (b *Backup) Run(ctx context.Context) error {
 	defer t.Stop()
 	defer close(b.closed)
 	// Reset status when finished
-	defer b.term.SetStatus([]string{""})
+	defer func() {
+		if b.term.CanUpdateStatus() {
+			b.term.SetStatus([]string{""})
+		}
+	}()
 
 	for {
 		select {
@@ -132,7 +136,7 @@ func (b *Backup) Run(ctx context.Context) error {
 		}
 
 		// limit update frequency
-		if time.Since(lastUpdate) < b.MinUpdatePause {
+		if time.Since(lastUpdate) < b.MinUpdatePause || b.MinUpdatePause == 0 {
 			continue
 		}
 		lastUpdate = time.Now()

internal/ui/termstatus/status.go

@@ -78,6 +78,11 @@ func New(wr io.Writer, errWriter io.Writer, disableStatus bool) *Terminal {
 	return t
 }
 
+// CanUpdateStatus return whether the status output is updated in place.
+func (t *Terminal) CanUpdateStatus() bool {
+	return t.canUpdateStatus
+}
+
 // Run updates the screen. It should be run in a separate goroutine. When
 // ctx is cancelled, the status lines are cleanly removed.
 func (t *Terminal) Run(ctx context.Context) {
@@ -203,8 +208,15 @@ func (t *Terminal) runWithoutStatus(ctx context.Context) {
 				fmt.Fprintf(os.Stderr, "flush failed: %v\n", err)
 			}
 
-		case <-t.status:
+		case stat := <-t.status:
-			// discard status lines
+			for _, line := range stat.lines {
+				// ensure that each line ends with newline
+				withNewline := strings.TrimRight(line, "\n") + "\n"
+				fmt.Fprint(t.wr, withNewline)
+			}
+			if err := t.wr.Flush(); err != nil {
+				fmt.Fprintf(os.Stderr, "flush failed: %v\n", err)
+			}
 		}
 	}
 }