read-tree -m A B: prime cache-tree from the switched-to tree

When switching to a new branch with "read-tree -m A B", the resulting
index must match tree B and we can prime the cache tree with it.

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

diff --git a/builtin-read-tree.c b/builtin-read-tree.c
index 9cd7d0738ed7018737196f03aa01c7bc7f720e26..391d709704320dba7a918fdd79b68c6c604d33b2 100644 (file)
--- a/builtin-read-tree.c
+++ b/builtin-read-tree.c
@@ -199,9 +199,14 @@ int cmd_read_tree(int argc, const char **argv, const char *unused_prefix)
         * "-m ent" or "--reset ent" form), we can obtain a fully
         * valid cache-tree because the index must match exactly
         * what came from the tree.
+        *
+        * The same holds true if we are switching between two trees
+        * using read-tree -m A B.  The index must match B after that.
         */
        if (nr_trees == 1 && !opts.prefix)
                prime_cache_tree(&active_cache_tree, trees[0]);
+       else if (nr_trees == 2 && opts.merge)
+               prime_cache_tree(&active_cache_tree, trees[1]);
 
        if (write_cache(newfd, active_cache, active_nr) ||
            commit_locked_index(&lock_file))