patch 8.0.0237: when 'wildoptions' is "tagfile" completion may not work

Problem:    When setting wildoptions=tagfile the completion context is not set
            correctly. (desjardins)
Solution:   Check for EXPAND_TAGS_LISTFILES. (Christian Brabandt, closes #1399)

src/ex_getln.c

@@ -4366,7 +4366,9 @@ addstar(
 		|| context == EXPAND_OWNSYNTAX
 		|| context == EXPAND_FILETYPE
 		|| context == EXPAND_PACKADD
-		|| (context == EXPAND_TAGS && fname[0] == '/'))
+		|| ((context == EXPAND_TAGS_LISTFILES
+			|| context == EXPAND_TAGS)
+		    && fname[0] == '/'))
 	    retval = vim_strnsave(fname, len);
 	else
 	{

src/testdir/test_cmdline.vim

@@ -295,3 +295,14 @@ func Test_illegal_address()
   2;')
   quit
 endfunc
+
+func Test_cmdline_complete_wildoptions()
+  help
+  call feedkeys(":tag /\<c-a>\<c-b>\"\<cr>", 'tx')
+  let a = join(sort(split(@:)),' ')
+  set wildoptions=tagfile
+  call feedkeys(":tag /\<c-a>\<c-b>\"\<cr>", 'tx')
+  let b = join(sort(split(@:)),' ')
+  call assert_equal(a, b)
+  bw!
+endfunc

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    237,
 /**/
     236,
 /**/