perf tools: Add the bash completion for listing subsubcommands of perf trace

The bash completion does not support listing subsubcommands for 'perf
trace <TAB>', so fix it.

Example:

Before this patch:

$ perf trace <TAB>
$

As shown above, the subsubcommands of perf trace does not come out.

After this patch:

$ perf trace <TAB>
record

As shown above, the subsubcommands of perf trace can come out now.

Signed-off-by: Yunlong Song <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Wang Nan <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/builtin-trace.c

···
 
 int cmd_trace(int argc, const char **argv, const char *prefix __maybe_unused)
 {
-	const char * const trace_usage[] = {
+	const char *trace_usage[] = {
 		"perf trace [<options>] [<command>]",
 		"perf trace [<options>] -- <command> [<options>]",
 		"perf trace record [<options>] [<command>]",
···
 	OPT_BOOLEAN(0, "syscalls", &trace.trace_syscalls, "Trace syscalls"),
 	OPT_END()
 	};
+	const char * const trace_subcommands[] = { "record", NULL };
 	int err;
 	char bf[BUFSIZ];
 
···
 		goto out;
 	}
 
-	argc = parse_options(argc, argv, trace_options, trace_usage,
-			     PARSE_OPT_STOP_AT_NON_OPTION);
+	argc = parse_options_subcommand(argc, argv, trace_options, trace_subcommands,
+				 trace_usage, PARSE_OPT_STOP_AT_NON_OPTION);
 
 	if (trace.trace_pgfaults) {
 		trace.opts.sample_address = true;

tools/perf/perf-completion.sh

···
 		((i--))
 	done
 }
+
 __perf_main ()
 {
 	local cmd
···
 			cmds=$($cmd --list-cmds)
 		fi
 		__perfcomp "$cmds" "$cur"
-	# List possible events for -e and --event option
-	elif [[ $prev == @("-e"|"--event") && $prev_skip_opts == @(record|stat|top) ]]; then
+	# List possible events for -e option
+	elif [[ $prev == @("-e"|"--event") &&
+		$prev_skip_opts == @(record|stat|top) ]]; then
 		evts=$($cmd list --raw-dump)
 		__perfcomp_colon "$evts" "$cur"
 	else
 		# List subcommands for perf commands
-		if [[ $prev_skip_opts == @(kvm|kmem|mem|lock|sched|data|help|script|test|timechart) ]]; then
+		if [[ $prev_skip_opts == @(kvm|kmem|mem|lock|sched|
+			|data|help|script|test|timechart|trace) ]]; then
 			subcmds=$($cmd $prev_skip_opts --list-cmds)
 			__perfcomp_colon "$subcmds" "$cur"
 		fi