treewide: rename tree to maybe_tree

Using the commit-graph file to walk commit history removes the large
cost of parsing commits during the walk. This exposes a performance
issue: lookup_tree() takes a large portion of the computation time,
even when Git never uses those trees.

In anticipation of lazy-loading these trees, rename the 'tree' member
of struct commit to 'maybe_tree'. This serves two purposes: it hints
at the future role of possibly being NULL even if the commit has a
valid tree, and it allows for unambiguous transformation from simple
member access (i.e. commit->maybe_tree) to method access.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/tree.c b/tree.c
index b224115..dbc5e0b 100644
--- a/tree.c
+++ b/tree.c
@@ -109,7 +109,7 @@ static int read_tree_1(struct tree *tree, struct strbuf *base,
 				    oid_to_hex(entry.oid),
 				    base->buf, entry.path);
 
-			oidcpy(&oid, &commit->tree->object.oid);
+			oidcpy(&oid, &commit->maybe_tree->object.oid);
 		}
 		else
 			continue;
@@ -248,7 +248,7 @@ struct tree *parse_tree_indirect(const struct object_id *oid)
 		if (obj->type == OBJ_TREE)
 			return (struct tree *) obj;
 		else if (obj->type == OBJ_COMMIT)
-			obj = &(((struct commit *) obj)->tree->object);
+			obj = &(((struct commit *) obj)->maybe_tree->object);
 		else if (obj->type == OBJ_TAG)
 			obj = ((struct tag *) obj)->tagged;
 		else