show doc: redirect user to git log manual instead of git diff-tree

While git show accepts options that apply to the git diff-tree command,
some options do not make sense in the context of git show.
The options of git show are handled using the machinery of git log.
The git log manual page is a better place to look into than git diff-tree
for options that are not in the git show manual page.

Signed-off-by: Han Young <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: hanyang-tony

Documentation/git-show.txt

@@ -26,7 +26,7 @@ with --name-only).
 
 For plain blobs, it shows the plain contents.
 
-The command takes options applicable to the 'git diff-tree' command to
+Some options that 'git log' command understands can be used to
 control how the changes the commit introduces are shown.
 
 This manual page describes only the most frequently used options.