submodule: fix segmentation fault in submodule--helper clone

diff --git a/builtin/worktree.c b/builtin/worktree.c
index 6b9c946693ff5e0127dd4a6d0f6c93ba84631edb..20cf67a549b0d293f42e7f7c21f8822d06aa9c7c 100644 (file)
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -334,9 +334,18 @@ static int add(int ac, const char **av, const char *prefix)
        branch = ac < 2 ? "HEAD" : av[1];
 
        opts.force_new_branch = !!new_branch_force;
-       if (opts.force_new_branch)
+       if (opts.force_new_branch) {
+               struct strbuf symref = STRBUF_INIT;
+
                opts.new_branch = new_branch_force;
 
+               if (!opts.force &&
+                   !strbuf_check_branch_ref(&symref, opts.new_branch) &&
+                   ref_exists(symref.buf))
+                       die_if_checked_out(symref.buf);
+               strbuf_release(&symref);
+       }
+
        if (ac < 2 && !opts.new_branch && !opts.detach) {
                int n;
                const char *s = worktree_basename(path, &n);