Merge pull request git-tips#156 from 0xmohit/fix-difftool-ex

Fix difftool example

Author: hemanth

README.md

@@ -728,7 +728,7 @@ git diff --word-diff
 
 ## Show changes using common diff tools.
 ```sh
-git difftool -t <commit1> <commit2> <path>
+git difftool [-t <tool>] <commit1> <commit2> <path>
 ```
 
 ## Don’t consider changes for tracked file.