trace2: avoid emitting 'def_param' set more than once

During nested alias expansion it is possible for
"trace2_cmd_list_config()" and "trace2_cmd_list_env_vars()"
to be called more than once.  This causes a full set of
'def_param' events to be emitted each time.  Let's avoid
that.

Add code to those two functions to only emit them once.

Signed-off-by: Jeff Hostetler <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: jeffhostetler

t/t0211-trace2-perf.sh

@@ -470,7 +470,7 @@ test_expect_success 'expect def_params during shell alias expansion' '
 	grep "d1|main|def_param|.*|ENV_PROP_FOO:blue" actual
 '
 
-test_expect_failure 'expect def_params during nested git alias expansion' '
+test_expect_success 'expect def_params during nested git alias expansion' '
 	test_when_finished "rm prop.perf actual" &&
 
 	test_config_global "trace2.configParams" "cfg.prop.*" &&

trace2.c

@@ -464,17 +464,29 @@ void trace2_cmd_alias_fl(const char *file, int line, const char *alias,
 
 void trace2_cmd_list_config_fl(const char *file, int line)
 {
+	static int emitted = 0;
+
 	if (!trace2_enabled)
 		return;
 
+	if (emitted)
+		return;
+	emitted = 1;
+
 	tr2_cfg_list_config_fl(file, line);
 }
 
 void trace2_cmd_list_env_vars_fl(const char *file, int line)
 {
+	static int emitted = 0;
+
 	if (!trace2_enabled)
 		return;
 
+	if (emitted)
+		return;
+	emitted = 1;
+
 	tr2_list_env_vars_fl(file, line);
 }