survey: add pathname of blob or tree to large_item_vec

Include the pathname of each blob or tree in the large_item_vec
to help identify the file or directory associated with the OID
and size information.

This pathname is computed during the treewalk, so it reflects the
first observed pathname seen for that OID during the traversal over
all of the refs.  Since the file or directory could have moved
(without being modified), there may be multiple "correct" pathnames
for a particular OID.  Since we do not control the ref traversal
order, we should consider it to be a "suggested pathname" for the OID.

Signed-off-by: Jeff Hostetler <jeffhostetler@github.com>

builtin/survey.c

@@ -327,6 +327,7 @@ static void incr_obj_hist_bin(struct obj_hist_bin *pbin,
 struct large_item {
 	uint64_t size;
 	struct object_id oid;
+	struct strbuf *name;
 };
 
 struct large_item_vec {
@@ -342,6 +343,7 @@ static struct large_item_vec *alloc_large_item_vec(const char *dimension_label,
 {
 	struct large_item_vec *vec;
 	size_t flex_len = nr_items * sizeof(struct large_item);
+	size_t k;
 
 	if (!nr_items)
 		return NULL;
@@ -351,20 +353,35 @@ static struct large_item_vec *alloc_large_item_vec(const char *dimension_label,
 	vec->item_label = strdup(item_label);
 	vec->nr_items = nr_items;
 
+	for (k = 0; k < nr_items; k++) {
+		struct strbuf *p = xcalloc(1, sizeof(struct strbuf));
+		strbuf_init(p, 0);
+		vec->items[k].name = p;
+	}
+
 	return vec;
 }
 
 static void free_large_item_vec(struct large_item_vec *vec)
 {
+	size_t k;
+
+	for (k = 0; k < vec->nr_items; k++) {
+		strbuf_release(vec->items[k].name);
+		free(vec->items[k].name);
+	}
+
 	free(vec->dimension_label);
 	free(vec->item_label);
 	free(vec);
 }
 
 static void maybe_insert_large_item(struct large_item_vec *vec,
 				    uint64_t size,
-				    struct object_id *oid)
+				    struct object_id *oid,
+				    const char *name)
 {
+	struct strbuf *pbuf_temp;
 	size_t rest_len;
 	size_t k;
 
@@ -383,7 +400,17 @@ static void maybe_insert_large_item(struct large_item_vec *vec,
 		if (size < vec->items[k].size)
 			continue;
 
-		/* push items[k..] down one and insert it here */
+		/*
+		 * The last large_item in the vector is about to be
+		 * overwritten by the previous one during the shift.
+		 * Steal its allocated strbuf and reuse it.
+		 */
+		pbuf_temp = vec->items[vec->nr_items - 1].name;
+		strbuf_reset(pbuf_temp);
+		if (name && *name)
+			strbuf_addstr(pbuf_temp, name);
+
+		/* push items[k..] down one and insert data for this item here */
 
 		rest_len = (vec->nr_items - k - 1) * sizeof(struct large_item);
 		if (rest_len)
@@ -392,6 +419,9 @@ static void maybe_insert_large_item(struct large_item_vec *vec,
 		memset(&vec->items[k], 0, sizeof(struct large_item));
 		vec->items[k].size = size;
 		oidcpy(&vec->items[k].oid, oid);
+
+		vec->items[k].name = pbuf_temp;
+
 		return;
 	}
 }
@@ -665,15 +695,15 @@ static void traverse_commit_cb(struct commit *commit, void *data)
 
 	k = commit_list_count(commit->parents);
 
-	maybe_insert_large_item(psc->vec_largest_by_nr_parents, k, &commit->object.oid);
-	maybe_insert_large_item(psc->vec_largest_by_size_bytes, object_length, &commit->object.oid);
+	maybe_insert_large_item(psc->vec_largest_by_nr_parents, k, &commit->object.oid, NULL);
+	maybe_insert_large_item(psc->vec_largest_by_size_bytes, object_length, &commit->object.oid, NULL);
 
 	if (k >= PBIN_VEC_LEN)
 		k = PBIN_VEC_LEN - 1;
 	psc->parent_cnt_pbin[k]++;
 }
 
-static void traverse_object_cb_tree(struct object *obj)
+static void traverse_object_cb_tree(struct object *obj, const char *name)
 {
 	struct survey_stats_trees *pst = &survey_stats.trees;
 	unsigned long object_length;
@@ -697,21 +727,21 @@ static void traverse_object_cb_tree(struct object *obj)
 
 	pst->sum_entries += nr_entries;
 
-	maybe_insert_large_item(pst->vec_largest_by_nr_entries, nr_entries, &obj->oid);
-	maybe_insert_large_item(pst->vec_largest_by_size_bytes, object_length, &obj->oid);
+	maybe_insert_large_item(pst->vec_largest_by_nr_entries, nr_entries, &obj->oid, name);
+	maybe_insert_large_item(pst->vec_largest_by_size_bytes, object_length, &obj->oid, name);
 
 	qb = qbin(nr_entries);
 	incr_obj_hist_bin(&pst->entry_qbin[qb], object_length, disk_sizep);
 }
 
-static void traverse_object_cb_blob(struct object *obj)
+static void traverse_object_cb_blob(struct object *obj, const char *name)
 {
 	struct survey_stats_blobs *psb = &survey_stats.blobs;
 	unsigned long object_length;
 
 	fill_in_base_object(&psb->base, obj, OBJ_BLOB, &object_length, NULL);
 
-	maybe_insert_large_item(psb->vec_largest_by_size_bytes, object_length, &obj->oid);
+	maybe_insert_large_item(psb->vec_largest_by_size_bytes, object_length, &obj->oid, name);
 }
 
 static void traverse_object_cb(struct object *obj, const char *name, void *data)
@@ -721,10 +751,10 @@ static void traverse_object_cb(struct object *obj, const char *name, void *data)
 
 	switch (obj->type) {
 	case OBJ_TREE:
-		traverse_object_cb_tree(obj);
+		traverse_object_cb_tree(obj, name);
 		return;
 	case OBJ_BLOB:
-		traverse_object_cb_blob(obj);
+		traverse_object_cb_blob(obj, name);
 		return;
 	case OBJ_TAG:    /* ignore     -- counted when loading REFS */
 	case OBJ_COMMIT: /* ignore/bug -- seen in the other callback */
@@ -1197,6 +1227,8 @@ static void write_large_item_vec_json(struct json_writer *jw,
 			{
 				jw_object_intmax(jw, vec->item_label, pk->size);
 				jw_object_string(jw, "oid", oid_to_hex(&pk->oid));
+				if (pk->name->len)
+					jw_object_string(jw, "name", pk->name->buf);
 			}
 			jw_end(jw);
 		}