perf tools: Provide help for subset of options

Some tools have a lot of options, so, providing a way to show help just
for some of them may come handy:

  $ perf report -h --tui

   Usage: perf report [<options>]

        --tui             Use the TUI interface

  $ perf report -h --tui --showcpuutilization -b -c

   Usage: perf report [<options>]

    -b, --branch-stack    use branch records for per branch histogram filling
    -c, --comms <comm[,comm...]>
                          only consider symbols in these comms
        --showcpuutilization
                          Show sample percentage for different cpu modes
        --tui             Use the TUI interface

  $

Using it with perf bash completion is also handy, just make sure you
source the needed file:

  $ . ~/git/linux/tools/perf/perf-completion.sh

Then press tab/tab after -- to see a list of options, put them after -h
and only the options chosen will have its help presented:

  $ perf report -h --
  --asm-raw              --demangle-kernel      --group
  --kallsyms             --pretty               --stdio
  --branch-history       --disassembler-style   --gtk
  --max-stack            --showcpuutilization   --symbol-filter
  --branch-stack         --dsos                 --header
  --mem-mode             --show-info            --symbols
  --call-graph           --dump-raw-trace       --header-only
  --modules              --show-nr-samples      --symfs
  --children             --exclude-other        --hide-unresolved
  --objdump              --show-ref-call-graph  --threads
  --column-widths        --fields               --ignore-callees
  --parent               --show-total-period    --tid
  --comms                --field-separator      --input
  --percentage           --socket-filter        --tui
  --cpu                  --force                --inverted
  --percent-limit        --sort                 --verbose
  --demangle             --full-source-path     --itrace
  --pid                  --source               --vmlinux
  $ perf report -h --socket-filter

   Usage: perf report [<options>]

      --socket-filter <n>
                  only show processor socket that match with this filter

Suggested-by: Ingo Molnar <mingo@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Chandler Carruth <chandlerc@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-83mcdd3wj0379jcgea8w0fxa@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/parse-options.c

@@ -373,7 +373,8 @@ void parse_options_start(struct parse_opt_ctx_t *ctx,
 }
 
 static int usage_with_options_internal(const char * const *,
-				       const struct option *, int);
+				       const struct option *, int,
+				       struct parse_opt_ctx_t *);
 
 int parse_options_step(struct parse_opt_ctx_t *ctx,
 		       const struct option *options,
@@ -397,8 +398,9 @@ int parse_options_step(struct parse_opt_ctx_t *ctx,
 
 		if (arg[1] != '-') {
 			ctx->opt = ++arg;
-			if (internal_help && *ctx->opt == 'h')
-				return usage_with_options_internal(usagestr, options, 0);
+			if (internal_help && *ctx->opt == 'h') {
+				return usage_with_options_internal(usagestr, options, 0, ctx);
+			}
 			switch (parse_short_opt(ctx, options)) {
 			case -1:
 				return parse_options_usage(usagestr, options, arg, 1);
@@ -413,7 +415,7 @@ int parse_options_step(struct parse_opt_ctx_t *ctx,
 				check_typos(arg, options);
 			while (ctx->opt) {
 				if (internal_help && *ctx->opt == 'h')
-					return usage_with_options_internal(usagestr, options, 0);
+					return usage_with_options_internal(usagestr, options, 0, ctx);
 				arg = ctx->opt;
 				switch (parse_short_opt(ctx, options)) {
 				case -1:
@@ -446,9 +448,9 @@ int parse_options_step(struct parse_opt_ctx_t *ctx,
 
 		arg += 2;
 		if (internal_help && !strcmp(arg, "help-all"))
-			return usage_with_options_internal(usagestr, options, 1);
+			return usage_with_options_internal(usagestr, options, 1, ctx);
 		if (internal_help && !strcmp(arg, "help"))
-			return usage_with_options_internal(usagestr, options, 0);
+			return usage_with_options_internal(usagestr, options, 0, ctx);
 		if (!strcmp(arg, "list-opts"))
 			return PARSE_OPT_LIST_OPTS;
 		if (!strcmp(arg, "list-cmds"))
@@ -682,8 +684,27 @@ out:
 	return ordered;
 }
 
+static bool option__in_argv(const struct option *opt, const struct parse_opt_ctx_t *ctx)
+{
+	int i;
+
+	for (i = 1; i < ctx->argc; ++i) {
+		const char *arg = ctx->argv[i];
+
+		if (arg[0] != '-')
+			continue;
+
+		if (arg[1] == opt->short_name ||
+		    (arg[1] == '-' && opt->long_name && strcmp(opt->long_name, arg + 2) == 0))
+			return true;
+	}
+
+	return false;
+}
+
 int usage_with_options_internal(const char * const *usagestr,
-				const struct option *opts, int full)
+				const struct option *opts, int full,
+				struct parse_opt_ctx_t *ctx)
 {
 	struct option *ordered;
 
@@ -707,8 +728,11 @@ int usage_with_options_internal(const char * const *usagestr,
 	if (ordered)
 		opts = ordered;
 
-	for (  ; opts->type != OPTION_END; opts++)
+	for (  ; opts->type != OPTION_END; opts++) {
+		if (ctx && ctx->argc > 1 && !option__in_argv(opts, ctx))
+			continue;
 		print_option_help(opts, full);
+	}
 
 	fputc('\n', stderr);
 
@@ -721,7 +745,7 @@ void usage_with_options(const char * const *usagestr,
 			const struct option *opts)
 {
 	exit_browser(false);
-	usage_with_options_internal(usagestr, opts, 0);
+	usage_with_options_internal(usagestr, opts, 0, NULL);
 	exit(129);
 }