perf tools: Search for more options when passing args to -h

Recently 'perf <tool> -h' was made aware of arguments and would show
just the help for the arguments specified, but that required a strict
form, i.e.:

$ perf -h --tui

worked, but:

$ perf -h tui

didn't.

Make it support both cases and also look at the option help when neither
matches, so that he following examples works:

$ perf report -h interface

Usage: perf report [<options>]

--gtk Use the GTK2 interface
--stdio Use the stdio interface
--tui Use the TUI interface

$ perf report -h stack

Usage: perf report [<options>]

-g, --call-graph <print_type,threshold[,print_limit],order,
sort_key[,branch]>
Display call graph (stack chain/backtrace):

print_type: call graph printing style (graph|flat|fractal|none)
threshold: minimum call graph inclusion threshold (<percent>)
print_limit: maximum number of call graph entry (<number>)
order: call graph order (caller|callee)
sort_key: call graph sort key (function|address)
branch: include last branch info to call graph (branch)

Default: graph,0.5,caller,function
--max-stack <n> Set the maximum stack depth when parsing the
callchain, anything beyond the specified depth
will be ignored. Default: 127
$

Suggested-by: Ingo Molnar <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Brendan Gregg <[e-mail]>
Cc: Chandler Carruth <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Frederic Weisbecker <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Stephane Eranian <[e-mail]>
Cc: Wang Nan <[e-mail]>
Link: http://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/parse-options.c

···
 	for (i = 1; i < ctx->argc; ++i) {
 		const char *arg = ctx->argv[i];
 
-		if (arg[0] != '-')
+		if (arg[0] != '-') {
+			if (arg[1] == '\0') {
+				if (arg[0] == opt->short_name)
+					return true;
+				continue;
+			}
+
+			if (opt->long_name && strcmp(opt->long_name, arg) == 0)
+				return true;
+
+			if (opt->help && strcasestr(opt->help, arg) != NULL)
+				return true;
+
 			continue;
+		}
 
 		if (arg[1] == opt->short_name ||
 		    (arg[1] == '-' && opt->long_name && strcmp(opt->long_name, arg + 2) == 0))