cache-tree: use trace2 in cache_tree_update()

This matches a trace_performance_enter()/trace_performance_leave() pair
added by 0d1ed59 (unpack-trees: add performance tracing, 2018-08-18).

Signed-off-by: Derrick Stolee <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: derrickstolee

cache-tree.c

@@ -442,7 +442,9 @@ int cache_tree_update(struct index_state *istate, int flags)
 	if (i)
 		return i;
 	trace_performance_enter();
+	trace2_region_enter("cache_tree", "update", the_repository);
 	i = update_one(it, cache, entries, "", 0, &skip, flags);
+	trace2_region_leave("cache_tree", "update", the_repository);
 	trace_performance_leave("cache_tree_update");
 	if (i < 0)
 		return i;