perf config: Add '--system' and '--user' options to select which config file is used

The '--system' option means $(sysconfdir)/perfconfig and '--user' means
$HOME/.perfconfig. If none is used, both system and user config file are
read.  E.g.:

    # perf config [<file-option>] [options]

    With an specific config file:

    # perf config --user | --system

    or both user and system config file:

    # perf config

Signed-off-by: Taeung Song <treeze.taeung@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/1455126685-32367-2-git-send-email-treeze.taeung@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/builtin-config.c b/tools/perf/builtin-config.c
index f04e804..c42448e 100644
--- a/tools/perf/builtin-config.c
+++ b/tools/perf/builtin-config.c
@@ -13,8 +13,10 @@
 #include "util/util.h"
 #include "util/debug.h"
 
+static bool use_system_config, use_user_config;
+
 static const char * const config_usage[] = {
-	"perf config [options]",
+	"perf config [<file-option>] [options]",
 	NULL
 };
 
@@ -25,6 +27,8 @@
 static struct option config_options[] = {
 	OPT_SET_UINT('l', "list", &actions,
 		     "show current config variables", ACTION_LIST),
+	OPT_BOOLEAN(0, "system", &use_system_config, "use system config file"),
+	OPT_BOOLEAN(0, "user", &use_user_config, "use user config file"),
 	OPT_END()
 };
 
@@ -42,10 +46,23 @@
 int cmd_config(int argc, const char **argv, const char *prefix __maybe_unused)
 {
 	int ret = 0;
+	char *user_config = mkpath("%s/.perfconfig", getenv("HOME"));
 
 	argc = parse_options(argc, argv, config_options, config_usage,
 			     PARSE_OPT_STOP_AT_NON_OPTION);
 
+	if (use_system_config && use_user_config) {
+		pr_err("Error: only one config file at a time\n");
+		parse_options_usage(config_usage, config_options, "user", 0);
+		parse_options_usage(NULL, config_options, "system", 0);
+		return -1;
+	}
+
+	if (use_system_config)
+		config_exclusive_filename = perf_etc_perfconfig();
+	else if (use_user_config)
+		config_exclusive_filename = user_config;
+
 	switch (actions) {
 	case ACTION_LIST:
 		if (argc) {
@@ -53,9 +70,13 @@
 			parse_options_usage(config_usage, config_options, "l", 1);
 		} else {
 			ret = perf_config(show_config, NULL);
-			if (ret < 0)
+			if (ret < 0) {
+				const char * config_filename = config_exclusive_filename;
+				if (!config_exclusive_filename)
+					config_filename = user_config;
 				pr_err("Nothing configured, "
-				       "please check your ~/.perfconfig file\n");
+				       "please check your %s \n", config_filename);
+			}
 		}
 		break;
 	default: