Merge pull request #73 from kyoh86/desc-options-usage

Describe how the options be used by ddu.vim

doc/ddu.txt

@@ -1355,6 +1355,9 @@ FAQ 6:							|ddu-faq-6|
 FAQ 7:							|ddu-faq-7|
 	I want to execute grep action from items.
 
+FAQ 8:							|ddu-faq-8|
+	How ddu.vim use options?
+
 
 ------------------------------------------------------------------------------
                                                                    *ddu-faq-1*
@@ -1434,6 +1437,22 @@ A: The example is here. >
 	      \ })
 	endfunction
 <
+							*ddu-faq-8*
+Q: How ddu.vim use options?
+
+	There're 4 layers of options for the ddu.vim in order of priority:
+
+		user: as passed in |ddu#start()| or |ddu#get_items()|.
+		local: as assembled by |ddu#custom#patch_local()| with a name.
+		global: as assembled by |ddu#custom#patch_global()|.
+		default: as described in each |ddu-options|.
+
+	ddu.vim merges them recursively.
+
+	The |ddu-option-name| describes the name which local option be used.
+	And |ddu-option-name| value is also decided by user, global and
+	default options.
+
 
 ==============================================================================
 COMPATIBILITY                                              *ddu-compatibility*