read-tree: teach 1-way merege and plain read to prime cache-tree.

This teaches read-tree to fully populate valid cache-tree when
reading a tree from scratch, or reading a single tree into an
existing index, reusing only the cached stat information (i.e.
one-way merge).  We have already taught update-index about cache-tree,
so "git checkout" followed by updates to a few path followed by
a "git commit" would become very efficient.

Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/cache-tree.h b/cache-tree.h
index c70a7699a9..5d824df2ec 100644
--- a/cache-tree.h
+++ b/cache-tree.h
@@ -20,6 +20,7 @@ struct cache_tree {
 struct cache_tree *cache_tree(void);
 void cache_tree_free(struct cache_tree **);
 void cache_tree_invalidate_path(struct cache_tree *, const char *);
+struct cache_tree_sub *cache_tree_sub(struct cache_tree *, const char *);
 
 void *cache_tree_write(struct cache_tree *root, unsigned long *size_p);
 struct cache_tree *cache_tree_read(const char *buffer, unsigned long size);