git-show-branch.txt: document --date-order option

Copy the description of date-order from rev-list-options.txt, and then
reword it to be commit specific. While we're at it, put <rev> <glob>...
on a new line to not exceed 80 characters.

Signed-off-by: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-show-branch.txt

@@ -8,10 +8,11 @@ git-show-branch - Show branches and their commits
 SYNOPSIS
 --------
 [verse]
-'git show-branch' [--all] [--remotes] [--topo-order] [--current]
+'git show-branch' [--all] [--remotes] [--topo-order | --date-order]
+		[--current] [--color | --no-color]
 		[--more=<n> | --list | --independent | --merge-base]
-		[--color | --no-color]
-		[--no-name | --sha1-name] [--topics] [<rev> | <glob>]...
+		[--no-name | --sha1-name] [--topics]
+		[<rev> | <glob>]...
 'git show-branch' (-g|--reflog)[=<n>[,<base>]] [--list] [<ref>]
 
 DESCRIPTION
@@ -58,6 +59,11 @@ OPTIONS
         appear in topological order (i.e., descendant commits
         are shown before their parents).
 
+--date-order::
+	This option is similar to '--topo-order' in the sense that no
+	parent comes before all of its children, but otherwise commits
+	are ordered according to their commit date.
+
 --sparse::
 	By default, the output omits merges that are reachable
 	from only one tip being shown.  This option makes them