trace2: redact URLs in alias events

trace2_cmd_alias_fl() passes its argument array directly to the targets.
A URL embedded in an ordinary alias definition, or passed through a
shell alias, can therefore appear in an alias event without the
redaction used for start, child_start, and exec events.

Redact the arguments before alias-event dispatch and release the
temporary array afterward.

Signed-off-by: Taylor Blau <ttaylorr@openai.com>

Author: ttaylorr-oai

t/t0212-trace2-event.sh

@@ -407,4 +407,11 @@ test_expect_success 'URL signature redaction can be disabled' '
 	test_grep "\"event\":\"error\".*sig=secret" trace.event
 '
 
+test_expect_success 'alias events redact URL signatures' '
+	test_when_finished "rm trace.event" &&
+	test_config alias.redact "rev-parse --sq-quote https://example.com/?sig=secret" &&
+	GIT_TRACE2_EVENT="$(pwd)/trace.event" git redact >/dev/null &&
+	test_grep "\"event\":\"alias\".*sig=<REDACTED>" trace.event
+'
+
 test_done

trace2.c

@@ -560,14 +560,19 @@ void trace2_cmd_alias_fl(const char *file, int line, const char *alias,
 			 const char **argv)
 {
 	struct tr2_tgt *tgt_j;
+	const char **redacted;
 	int j;
 
 	if (!trace2_enabled)
 		return;
 
+	redacted = redact_argv(argv);
+
 	for_each_wanted_builtin (j, tgt_j)
 		if (tgt_j->pfn_alias_fl)
-			tgt_j->pfn_alias_fl(file, line, alias, argv);
+			tgt_j->pfn_alias_fl(file, line, alias, redacted);
+
+	free_redacted_argv(redacted, argv);
 }
 
 void trace2_cmd_list_config_fl(const char *file, int line)