checkout branch: prime cache-tree fully

When switching to another branch, the earlier code relied on incremental
invalidation of cache-tree entries to degrade it.  While it is not wrong
per-se, we know that the resulting index must fully match the branch we
are switching to unless the -m (merge) option is used.

We should simply fully re-prime the cache-tree using the new tree object
in such a case.  And for safety, invalidate the cache-tree as a whole in
other cases.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin-checkout.c b/builtin-checkout.c
index ffdb33aef596740890362a0e237d33131a906f45..efa1ebfe07f99e5092710fb951f9e23f16dd1b85 100644 (file)
--- a/builtin-checkout.c
+++ b/builtin-checkout.c
@@ -368,14 +368,17 @@ static int merge_working_tree(struct checkout_opts *opts,
        int ret;
        struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
        int newfd = hold_locked_index(lock_file, 1);
+       int reprime_cache_tree = 0;
 
        if (read_cache() < 0)
                return error("corrupt index file");
 
+       cache_tree_free(&active_cache_tree);
        if (opts->force) {
                ret = reset_tree(new->commit->tree, opts, 1);
                if (ret)
                        return ret;
+               reprime_cache_tree = 1;
        } else {
                struct tree_desc trees[2];
                struct tree *tree;
@@ -411,7 +414,9 @@ static int merge_working_tree(struct checkout_opts *opts,
                init_tree_desc(&trees[1], tree->buffer, tree->size);
 
                ret = unpack_trees(2, trees, &topts);
-               if (ret == -1) {
+               if (ret != -1) {
+                       reprime_cache_tree = 1;
+               } else {
                        /*
                         * Unpack couldn't do a trivial merge; either
                         * give up or do a real merge, depending on
@@ -455,6 +460,8 @@ static int merge_working_tree(struct checkout_opts *opts,
                }
        }
 
+       if (reprime_cache_tree)
+               prime_cache_tree(&active_cache_tree, new->commit->tree);
        if (write_cache(newfd, active_cache, active_nr) ||
            commit_locked_index(lock_file))
                die("unable to write new index file");