make_transient_cache_entry(): optionally alloc from mem_pool

Allow make_transient_cache_entry() to optionally receive a mem_pool
struct in which it should allocate the entry. This will be used in the
following patch, to store some transient entries which should persist
until parallel checkout finishes.

Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/checkout--worker.c

@@ -39,7 +39,7 @@ static void packet_to_pc_item(const char *buffer, int len,
 	}
 
 	memset(pc_item, 0, sizeof(*pc_item));
-	pc_item->ce = make_empty_transient_cache_entry(fixed_portion->name_len);
+	pc_item->ce = make_empty_transient_cache_entry(fixed_portion->name_len, NULL);
 	pc_item->ce->ce_namelen = fixed_portion->name_len;
 	pc_item->ce->ce_mode = fixed_portion->ce_mode;
 	memcpy(pc_item->ce->name, variant, pc_item->ce->ce_namelen);

builtin/checkout.c

@@ -291,7 +291,7 @@ static int checkout_merged(int pos, const struct checkout *state, int *nr_checko
 	if (write_object_file(result_buf.ptr, result_buf.size, blob_type, &oid))
 		die(_("Unable to add merge result for '%s'"), path);
 	free(result_buf.ptr);
-	ce = make_transient_cache_entry(mode, &oid, path, 2);
+	ce = make_transient_cache_entry(mode, &oid, path, 2, NULL);
 	if (!ce)
 		die(_("make_cache_entry failed for path '%s'"), path);
 	status = checkout_entry(ce, state, NULL, nr_checkouts);

builtin/difftool.c

@@ -323,7 +323,7 @@ static int checkout_path(unsigned mode, struct object_id *oid,
 	struct cache_entry *ce;
 	int ret;
 
-	ce = make_transient_cache_entry(mode, oid, path, 0);
+	ce = make_transient_cache_entry(mode, oid, path, 0, NULL);
 	ret = checkout_entry(ce, state, NULL, NULL);
 
 	discard_cache_entry(ce);

cache.h

@@ -356,16 +356,20 @@ struct cache_entry *make_empty_cache_entry(struct index_state *istate,
 					   size_t name_len);
 
 /*
- * Create a cache_entry that is not intended to be added to an index.
- * Caller is responsible for discarding the cache_entry
- * with `discard_cache_entry`.
+ * Create a cache_entry that is not intended to be added to an index. If
+ * `ce_mem_pool` is not NULL, the entry is allocated within the given memory
+ * pool. Caller is responsible for discarding "loose" entries with
+ * `discard_cache_entry()` and the memory pool with
+ * `mem_pool_discard(ce_mem_pool, should_validate_cache_entries())`.
  */
 struct cache_entry *make_transient_cache_entry(unsigned int mode,
 					       const struct object_id *oid,
 					       const char *path,
-					       int stage);
+					       int stage,
+					       struct mem_pool *ce_mem_pool);
 
-struct cache_entry *make_empty_transient_cache_entry(size_t name_len);
+struct cache_entry *make_empty_transient_cache_entry(size_t len,
+						     struct mem_pool *ce_mem_pool);
 
 /*
  * Discard cache entry.

read-cache.c

@@ -813,8 +813,11 @@ struct cache_entry *make_empty_cache_entry(struct index_state *istate, size_t le
 	return mem_pool__ce_calloc(find_mem_pool(istate), len);
 }
 
-struct cache_entry *make_empty_transient_cache_entry(size_t len)
+struct cache_entry *make_empty_transient_cache_entry(size_t len,
+						     struct mem_pool *ce_mem_pool)
 {
+	if (ce_mem_pool)
+		return mem_pool__ce_calloc(ce_mem_pool, len);
 	return xcalloc(1, cache_entry_size(len));
 }
 
@@ -848,8 +851,11 @@ struct cache_entry *make_cache_entry(struct index_state *istate,
 	return ret;
 }
 
-struct cache_entry *make_transient_cache_entry(unsigned int mode, const struct object_id *oid,
-					       const char *path, int stage)
+struct cache_entry *make_transient_cache_entry(unsigned int mode,
+					       const struct object_id *oid,
+					       const char *path,
+					       int stage,
+					       struct mem_pool *ce_mem_pool)
 {
 	struct cache_entry *ce;
 	int len;
@@ -860,7 +866,7 @@ struct cache_entry *make_transient_cache_entry(unsigned int mode, const struct o
 	}
 
 	len = strlen(path);
-	ce = make_empty_transient_cache_entry(len);
+	ce = make_empty_transient_cache_entry(len, ce_mem_pool);
 
 	oidcpy(&ce->oid, oid);
 	memcpy(ce->name, path, len);

unpack-trees.c

@@ -1034,7 +1034,7 @@ static struct cache_entry *create_ce_entry(const struct traverse_info *info,
 	size_t len = traverse_path_len(info, tree_entry_len(n));
 	struct cache_entry *ce =
 		is_transient ?
-		make_empty_transient_cache_entry(len) :
+		make_empty_transient_cache_entry(len, NULL) :
 		make_empty_cache_entry(istate, len);
 
 	ce->ce_mode = create_ce_mode(n->mode);