Update runtime files
diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index c93da54..dc68def 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -2872,6 +2872,10 @@
/home/user/vim/vim/src
< If {mods} is empty or an unsupported modifier is used then
{fname} is returned.
+ When {fname} is empty then with {mods} ":h" returns ".", so
+ that `:cd` can be used with it. This is different from
+ expand('%:h') without a buffer name, which returns an empty
+ string.
Note: Environment variables don't work in {fname}, use
|expand()| first then.