btrbk: add --pretty option: print lowercase column headings with separator line

ChangeLog

@@ -7,6 +7,10 @@ btrbk-current
       rate_limit_remote is set.
     - In order to mimic old behavior, replace rate_limit with
       rate_limit_remote, and read btrbk.conf(5).
+    - If you are using table output other than --format=raw in your
+      scripts, note that the column headings changed from pretty
+      two-line to (uppercase) one-line format. Either add --pretty
+      option to mimic old behavior, or adapt your scripts.
   * Dropped run-time dependency on "pv" (in favor of "mbuffer").
   * Combined stream_buffer and rate_limit: for rate_limit, use
     "mbuffer" (on local host) instead of "pv" (on source host).

btrbk

@@ -286,6 +286,7 @@ my @exclude_vf;
 my $do_dumper;
 my $show_progress = 0;
 my $output_format;
+my $output_pretty = 0;
 my $lockfile;
 my $tlog_fh;
 my $syslog_enabled = 0;
@@ -4673,7 +4674,7 @@ sub print_formatted(@)
   my %args = @_;
   my $title = $args{title};
   my $format = $args{output_format} || $output_format || $default_format;
-  my $pretty = $args{pretty};
+  my $pretty = $args{pretty} // $output_pretty;
   my $key_defs = $table_formats{$format_key}->{$format};
   my $ralign = $table_formats{$format_key}->{RALIGN} // {};
   my $fh = $args{outfile} // *STDOUT;
@@ -4943,6 +4944,7 @@ MAIN:
     'table|t'            => sub { $output_format = "table" },
     'long|L'             => sub { $output_format = "long" },
     'format=s'           => \$output_format,
+    'pretty'             => \$output_pretty,
     'print-schedule|S'   => \$print_schedule,
     'lockfile=s'         => \$lockfile_cmdline,
     'override=s'         => \@config_override_cmdline,  # e.g. --override=incremental=no

doc/btrbk.1.asciidoc

@@ -20,7 +20,7 @@ btrbk [-h|--help] [--version]
       [-c|--config <file>] [-n|--dry-run] [--exclude <filter>]
       [-p|--preserve] [--preserve-snapshots] [--preserve-backups]
       [-v|--verbose] [-q|--quiet] [-l|--loglevel <level>]
-      [-t|--table] [--format <output-format>]
+      [-t|--table] [--format <output-format>] [--pretty]
       [-S|--print-schedule] [--progress]
       [--lockfile <file>]
       [--override <config_option>=<value>]
@@ -126,6 +126,10 @@ OPTIONS
     output format for *run*, *snapshot*, *resume*, *prune*, *archive*
     and *list* commands. Useful for further exporting/scripting.
 
+--pretty::
+    Print table output with lowercase, underlined column headings
+    (instead of single-line uppercase headings).
+
 -S, --print-schedule::
     Print detailed scheduler information on *run*, *snapshot*,
     *resume*, *prune* and *archive* commands. Use the '--format'