Merge branch 'tn/fetch-pack-trace-packfile-uri' into next

The process of downloading packfile URIs in protocol v2 has been
instrumented with a Trace2 region.  This visibility allows tracking
the cumulative time spent downloading external packs and the number
of advertised URIs without emitting a separate event per pack.

* tn/fetch-pack-trace-packfile-uri:
  fetch-pack: trace packfile URI downloads

fetch-pack.c

@@ -1853,6 +1853,13 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 		}
 	}
 
+	if (packfile_uris.nr) {
+		trace2_region_enter("fetch-pack", "packfile-uris",
+				    the_repository);
+		trace2_data_intmax("fetch-pack", the_repository,
+				   "packfile-uris/count", packfile_uris.nr);
+	}
+
 	for (i = 0; i < packfile_uris.nr; i++) {
 		bool created_keep;
 		int j;
@@ -1906,6 +1913,11 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 							 repo_get_object_directory(the_repository),
 							 packhash));
 	}
+
+	if (packfile_uris.nr)
+		trace2_region_leave("fetch-pack", "packfile-uris",
+				    the_repository);
+
 	string_list_clear(&packfile_uris, 0);
 	strvec_clear(&index_pack_args);
 

t/t5702-protocol-v2.sh

@@ -1223,7 +1223,7 @@ configure_exclusion () {
 
 test_expect_success 'part of packfile response provided as URI' '
 	P="$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
-	rm -rf "$P" http_child log &&
+	rm -rf "$P" http_child log trace2 &&
 
 	git init "$P" &&
 	git -C "$P" config "uploadpack.allowsidebandall" "true" &&
@@ -1238,10 +1238,15 @@ test_expect_success 'part of packfile response provided as URI' '
 	configure_exclusion "$P" other-blob >h2 &&
 
 	GIT_TRACE=1 GIT_TRACE_PACKET="$(pwd)/log" GIT_TEST_SIDEBAND_ALL=1 \
+	GIT_TRACE2_EVENT="$(pwd)/trace2" \
 	git -c protocol.version=2 \
 		-c fetch.uriprotocols=http,https \
 		clone "$HTTPD_URL/smart/http_parent" http_child &&
 
+	test_grep \"event\":\"region_enter\".*\"label\":\"packfile-uris\" trace2 &&
+	test_grep \"key\":\"packfile-uris/count\",\"value\":\"2\" trace2 &&
+	test_grep \"event\":\"region_leave\".*\"label\":\"packfile-uris\" trace2 &&
+
 	# Ensure that my-blob and other-blob are in separate packfiles.
 	for idx in http_child/.git/objects/pack/*.idx
 	do