http: support omitting data from traces

GIT_TRACE_CURL provides a way to debug what is being sent and received
over HTTP, with automatic redaction of sensitive information. But it
also logs data transmissions, which significantly increases the log file
size, sometimes unnecessarily. Add an option "GIT_TRACE_CURL_NO_DATA" to
allow the user to omit such data transmissions.
Signed-off-by: NJonathan Tan <jonathantanmy@google.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Documentation/git.txt

@@ -646,6 +646,10 @@ of clones and fetches.
 	variable.
 	See `GIT_TRACE` for available trace output options.
 
+`GIT_TRACE_CURL_NO_DATA`::
+	When a curl trace is enabled (see `GIT_TRACE_CURL` above), do not dump
+	data (that is, only dump info lines and headers).
+
 `GIT_REDACT_COOKIES`::
 	This can be set to a comma-separated list of strings. When a curl trace
 	is enabled (see `GIT_TRACE_CURL` above), whenever a "Cookies:" header

http.c

@@ -16,6 +16,7 @@
 #include "string-list.h"
 
 static struct trace_key trace_curl = TRACE_KEY_INIT(CURL);
+static int trace_curl_data = 1;
 static struct string_list cookies_to_redact = STRING_LIST_INIT_DUP;
 #if LIBCURL_VERSION_NUM >= 0x070a08
 long int git_curl_ipresolve = CURL_IPRESOLVE_WHATEVER;
@@ -695,24 +696,32 @@ static int curl_trace(CURL *handle, curl_infotype type, char *data, size_t size,
 		curl_dump_header(text, (unsigned char *)data, size, DO_FILTER);
 		break;
 	case CURLINFO_DATA_OUT:
-		text = "=> Send data";
-		curl_dump_data(text, (unsigned char *)data, size);
+		if (trace_curl_data) {
+			text = "=> Send data";
+			curl_dump_data(text, (unsigned char *)data, size);
+		}
 		break;
 	case CURLINFO_SSL_DATA_OUT:
-		text = "=> Send SSL data";
-		curl_dump_data(text, (unsigned char *)data, size);
+		if (trace_curl_data) {
+			text = "=> Send SSL data";
+			curl_dump_data(text, (unsigned char *)data, size);
+		}
 		break;
 	case CURLINFO_HEADER_IN:
 		text = "<= Recv header";
 		curl_dump_header(text, (unsigned char *)data, size, NO_FILTER);
 		break;
 	case CURLINFO_DATA_IN:
-		text = "<= Recv data";
-		curl_dump_data(text, (unsigned char *)data, size);
+		if (trace_curl_data) {
+			text = "<= Recv data";
+			curl_dump_data(text, (unsigned char *)data, size);
+		}
 		break;
 	case CURLINFO_SSL_DATA_IN:
-		text = "<= Recv SSL data";
-		curl_dump_data(text, (unsigned char *)data, size);
+		if (trace_curl_data) {
+			text = "<= Recv SSL data";
+			curl_dump_data(text, (unsigned char *)data, size);
+		}
 		break;
 
 	default:		/* we ignore unknown types by default */
@@ -857,6 +866,8 @@ static CURL *get_curl_handle(void)
 	if (getenv("GIT_CURL_VERBOSE"))
 		curl_easy_setopt(result, CURLOPT_VERBOSE, 1L);
 	setup_curl_trace(result);
+	if (getenv("GIT_TRACE_CURL_NO_DATA"))
+		trace_curl_data = 0;
 	if (getenv("GIT_REDACT_COOKIES")) {
 		string_list_split(&cookies_to_redact,
 				  getenv("GIT_REDACT_COOKIES"), ',', -1);

t/t5551-http-fetch-smart.sh

@@ -385,5 +385,17 @@ test_expect_success 'GIT_REDACT_COOKIES handles empty values' '
 	grep "Cookie:.*Foo=<redacted>" err
 '
 
+test_expect_success 'GIT_TRACE_CURL_NO_DATA prevents data from being traced' '
+	rm -rf clone &&
+	GIT_TRACE_CURL=true \
+		git clone $HTTPD_URL/smart/repo.git clone 2>err &&
+	grep "=> Send data" err &&
+
+	rm -rf clone &&
+	GIT_TRACE_CURL=true GIT_TRACE_CURL_NO_DATA=1 \
+		git clone $HTTPD_URL/smart/repo.git clone 2>err &&
+	! grep "=> Send data" err
+'
+
 stop_httpd
 test_done