updated for version 7.4.312

Problem:    Cannot figure out what argument list is being used for a window.
Solution:   Add the arglistid() function. (Marcin Szamotulski)

runtime/doc/eval.txt

@@ -1716,6 +1716,8 @@ append( {lnum}, {string})	Number	append {string} below line {lnum}
 append( {lnum}, {list})		Number	append lines {list} below line {lnum}
 argc()				Number	number of files in the argument list
 argidx()			Number	current index in the argument list
+arglistid( [{winnr}, [ {tabnr}]])
+				Number	argument list id
 argv( {nr})			String	{nr} entry of the argument list
 argv( )				List	the argument list
 asin( {expr})			Float	arc sine of {expr}
@@ -2103,6 +2105,18 @@ argc()		The result is the number of files in the argument list of the
 argidx()	The result is the current index in the argument list.  0 is
 		the first file.  argc() - 1 is the last one.  See |arglist|.
 
+							*arglistid()*
+arglistid([{winnr}, [ {tabnr} ]])
+		Return the argument list ID.  This is a number which
+		identifies the argument list being used.  Zero is used for the
+		global argument list.
+		Return zero if the arguments are invalid.
+
+		Without arguments use the current window.
+		With {winnr} only use this window in the current tab page.
+		With {winnr} and {tabnr} use the window in the specified tab
+		page.
+
 							*argv()*
 argv([{nr}])	The result is the {nr}th file in the argument list of the
 		current window.  See |arglist|.  "argv(0)" is the first one.

runtime/doc/usr_41.txt

@@ -772,6 +772,7 @@ Date and Time:				*date-functions* *time-functions*
 Buffers, windows and the argument list:
 	argc()			number of entries in the argument list
 	argidx()		current position in the argument list
+	arglistid()		get id of the argument list
 	argv()			get one entry from the argument list
 	bufexists()		check if a buffer exists
 	buflisted()		check if a buffer exists and is listed