doc: move rev-list option -<n> from git-log.txt to rev-list-options.txt

rev-list-options.txt is included in git-rev-list.txt. This makes sure
rev-list man page also shows that, and at one place, together with
equivalent options -n and --max-count.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-log.txt

@@ -24,10 +24,6 @@ each commit introduces are shown.
 OPTIONS
 -------
 
--<n>::
-	Limits the number of commits to show.
-	Note that this is a commit limiting option, see below.
-
 <since>..<until>::
 	Show only commits between the named two commits.  When
 	either <since> or <until> is omitted, it defaults to
@@ -137,6 +133,8 @@ Examples
 	This makes sense only when following a strict policy of merging all
 	topic branches when staying on a single integration branch.
 
+`git log -3`::
+	Limits the number of commits to show to 3.
 
 Discussion
 ----------

Documentation/rev-list-options.txt

@@ -8,7 +8,8 @@ ordering and formatting options, such as '--reverse'.
 
 --
 
--n 'number'::
+-<number>::
+-n <number>::
 --max-count=<number>::
 
 	Limit the number of commits to output.