Documentation: document the pager.* configuration setting

It was already documented in RelNotes-1.6.0, but not in the git-config
manual page.

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

Documentation/config.txt

@@ -978,6 +978,11 @@ pack.packSizeLimit::
 	can be overridden by the `\--max-pack-size` option of
 	linkgit:git-repack[1].
 
+pager.<cmd>::
+	Allows to set your own pager preferences for each command, overriding
+	the default. If `\--pager` or `\--no-pager` is specified on the command
+	line, it takes precedence over this option.
+
 pull.octopus::
 	The default merge strategy to use when pulling multiple branches
 	at once.