Add payloads, bitmaps to trace API

This is a proposed adjustment to the trace APIs.  This makes the
trace levels into a bitmask so that they can be selectively enabled
and adds a callback-level payload, plus a message-level payload.

This makes it easier for me to a GIT_TRACE_PERF callbacks that
are simply bypassed if the PERF level is not set.

tests/diff/diff_helpers.c

@@ -229,3 +229,22 @@ void diff_print_raw(FILE *fp, git_diff *diff)
 		git_diff_print(diff, GIT_DIFF_FORMAT_RAW,
 			git_diff_print_callback__to_file_handle, fp ? fp : stderr));
 }
+
+void diff_perf_track_stats(
+	git_trace_level_t level,
+	void *cb_payload,
+	void *msg_payload,
+	const char *msg)
+{
+	diff_perf *data = cb_payload;
+
+	if (!(level & GIT_TRACE_PERF))
+		return;
+
+	if (!strcmp("stat", msg))
+		data->stat_calls += msg_payload ? *((size_t *)msg_payload) : 1;
+	else if (!strcmp("submodule_lookup", msg))
+		data->submodule_lookups++;
+	else if (!strcmp("oid_calculation", msg))
+		data->oid_calcs++;
+}

tests/diff/diff_helpers.h

@@ -62,3 +62,17 @@ extern int diff_foreach_via_iterator(
 
 extern void diff_print(FILE *fp, git_diff *diff);
 extern void diff_print_raw(FILE *fp, git_diff *diff);
+
+#include "git2/trace.h"
+
+typedef struct {
+	size_t stat_calls;
+	size_t oid_calcs;
+	size_t submodule_lookups;
+} diff_perf;
+
+extern void diff_perf_track_stats(
+	git_trace_level_t level,
+	void *cb_payload,
+	void *msg_payload,
+	const char *msg);

tests/diff/workdir.c

@@ -1,40 +1,19 @@
 #include "clar_libgit2.h"
 #include "diff_helpers.h"
 #include "repository.h"
-#include <git2/trace.h>
 
 static git_repository *g_repo = NULL;
 
 #ifdef GIT_TRACE
-static struct {
-	size_t stat_calls;
-	size_t oid_calcs;
-	size_t submodule_lookups;
-} g_diff_perf;
-
-static void add_stats(git_trace_level_t level, const char *msg)
-{
-	const char *assign = strchr(msg, '=');
-
-	GIT_UNUSED(level);
-
-	if (!assign)
-		return;
-
-	if (!strncmp("stat", msg, (assign - msg)))
-		g_diff_perf.stat_calls += atoi(assign + 1);
-	else if (!strncmp("submodule_lookup", msg, (assign - msg)))
-		g_diff_perf.submodule_lookups += atoi(assign + 1);
-	else if (!strncmp("oid_calculation", msg, (assign - msg)))
-		g_diff_perf.oid_calcs += atoi(assign + 1);
-}
+static diff_perf g_diff_perf;
 #endif
 
 void test_diff_workdir__initialize(void)
 {
 #ifdef GIT_TRACE
 	memset(&g_diff_perf, 0, sizeof(g_diff_perf));
-	cl_git_pass(git_trace_set(GIT_TRACE_TRACE, add_stats));
+	cl_git_pass(git_trace_set(
+		GIT_TRACE_PERF, diff_perf_track_stats, &g_diff_perf));
 #endif
 }
 
@@ -42,7 +21,7 @@ void test_diff_workdir__cleanup(void)
 {
 	cl_git_sandbox_cleanup();
 #ifdef GIT_TRACE
-	cl_git_pass(git_trace_set(0, NULL));
+	cl_git_pass(git_trace_set(GIT_TRACE_NONE, NULL, NULL));
 #endif
 }