Update runtime files.
diff --git a/runtime/doc/cmdline.txt b/runtime/doc/cmdline.txt
index d2c8196..ae364c3 100644
--- a/runtime/doc/cmdline.txt
+++ b/runtime/doc/cmdline.txt
@@ -894,7 +894,8 @@
directory.
:. Reduce file name to be relative to current directory, if
possible. File name is unmodified if it is not below the
- current directory.
+ current directory, but on MS-Windows the drive is removed if
+ it is the current drive.
For maximum shortness, use ":~:.".
:h Head of the file name (the last component and any separators
removed). Cannot be used with :e, :r or :t.