cookie.d: mention that "-" as filename means stdin

Reported-by: Dongliang Mu
Fixes #2410

diff --git a/docs/cmdline-opts/cookie.d b/docs/cmdline-opts/cookie.d
index 383adda6e844251526f32a05a69a7a7dbd807e16..3ae697548ddab3d104331f2af5abbe8d93711325 100644 (file)
--- a/docs/cmdline-opts/cookie.d
+++ b/docs/cmdline-opts/cookie.d
@@ -12,7 +12,8 @@ If no '=' symbol is used in the argument, it is instead treated as a filename
 to read previously stored cookie from. This option also activates the cookie
 engine which will make curl record incoming cookies, which may be handy if
 you're using this in combination with the --location option or do multiple URL
-transfers on the same invoke.
+transfers on the same invoke. If the file name is exactly a minus ("-"), curl
+will instead the contents from stdin.
 
 The file format of the file to read cookies from should be plain HTTP headers
 (Set-Cookie style) or the Netscape/Mozilla cookie file format.