git-stash documentation: mention default options for 'list'

Signed-off-by: NMiklos Vajna <vmiklos@frugalware.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Documentation/git-stash.txt

@@ -66,7 +66,8 @@ stash@{1}: On master: 9cc0589... Add git-stash
 ----------------------------------------------------------------
 +
 The command takes options applicable to the 'git-log'
-command to control what is shown and how. See linkgit:git-log[1].
+command to control what is shown and how. If no options are set, the
+default is `-n 10`. See linkgit:git-log[1].
 
 show [<stash>]::