git-read-tree: -u without -m is meaningless. Don't allow it.

Also, documetn the "-u" in the usage string.

diff --git a/read-tree.c b/read-tree.c
index cf6d28e..fbd0da0 100644 (file)
--- a/read-tree.c
+++ b/read-tree.c
@@ -275,7 +275,7 @@ static void merge_cache(struct cache_entry **src, int nr, merge_fn_t fn)
        check_updates(active_cache, active_nr);
 }
 
-static char *read_tree_usage = "git-read-tree (<sha> | -m <sha1> [<sha2> [<sha3>]])";
+static char *read_tree_usage = "git-read-tree (<sha> | -m [-u] <sha1> [<sha2> [<sha3>]])";
 
 static struct cache_file cache_file;
 
@@ -320,6 +320,8 @@ int main(int argc, char **argv)
                        die("failed to unpack tree object %s", arg);
                stage++;
        }
+       if (update && !merge)
+               usage(read_tree_usage);
        if (merge) {
                static const merge_fn_t merge_function[] = {
                        [1] = oneway_merge,