Merge branch 'cc/delta-islands'

A few issues in the implementation of "delta-islands" feature has
been corrected.

* cc/delta-islands:
  pack-objects: fix off-by-one in delta-island tree-depth computation
  pack-objects: zero-initialize tree_depth/layer arrays
  pack-objects: fix tree_depth and layer invariants

builtin/pack-objects.c

@@ -2786,9 +2786,11 @@ static void show_object(struct object *obj, const char *name, void *data)
 
 	if (use_delta_islands) {
 		const char *p;
-		unsigned depth = 0;
+		unsigned depth;
 		struct object_entry *ent;
 
+		/* the empty string is a root tree, which is depth 0 */
+		depth = *name ? 1 : 0;
 		for (p = strchr(name, '/'); p; p = strchr(p + 1, '/'))
 			depth++;
 

git-compat-util.h

@@ -861,6 +861,7 @@ extern FILE *fopen_or_warn(const char *path, const char *mode);
 #define FREE_AND_NULL(p) do { free(p); (p) = NULL; } while (0)
 
 #define ALLOC_ARRAY(x, alloc) (x) = xmalloc(st_mult(sizeof(*(x)), (alloc)))
+#define CALLOC_ARRAY(x, alloc) (x) = xcalloc((alloc), sizeof(*(x)));
 #define REALLOC_ARRAY(x, alloc) (x) = xrealloc((x), st_mult(sizeof(*(x)), (alloc)))
 
 #define COPY_ARRAY(dst, src, n) copy_array((dst), (src), (n), sizeof(*(dst)) + \

pack-objects.h

@@ -412,7 +412,7 @@ static inline void oe_set_tree_depth(struct packing_data *pack,
 				     unsigned int tree_depth)
 {
 	if (!pack->tree_depth)
-		ALLOC_ARRAY(pack->tree_depth, pack->nr_objects);
+		CALLOC_ARRAY(pack->tree_depth, pack->nr_alloc);
 	pack->tree_depth[e - pack->objects] = tree_depth;
 }
 
@@ -429,7 +429,7 @@ static inline void oe_set_layer(struct packing_data *pack,
 				unsigned char layer)
 {
 	if (!pack->layer)
-		ALLOC_ARRAY(pack->layer, pack->nr_objects);
+		CALLOC_ARRAY(pack->layer, pack->nr_alloc);
 	pack->layer[e - pack->objects] = layer;
 }