+=head1 PROGRESS BARS
+
+Some (not all) long-running commands send progress notification
+messages as they are running. Guestfish turns these messages into
+progress bars.
+
+When a command that supports progress bars takes longer than two
+seconds to run, and if progress bars are enabled, then you will see
+one appearing below the command:
+
+ ><fs> copy-size /large-file /another-file 2048M
+ / 10% [#####-----------------------------------------] 00:30
+
+The spinner on the left hand side moves round once for every progress
+notification received from the backend. This is a (reasonably) golden
+assurance that the command is "doing something" even if the progress
+bar is not moving, because the command is able to send the progress
+notifications. When the bar reaches 100% and the command finishes,
+the spinner disappears.
+
+Progress bars are enabled by default when guestfish is used
+interactively. You can enable them even for non-interactive modes
+using I<--progress-bars>, and you can disable them completely using
+I<--no-progress-bars>.
+