FEAT_SIGNS: restore :signs wildmenu, and add test.

src/nvim/ex_getln.c

@@ -3697,6 +3697,7 @@ ExpandFromContext (
       {EXPAND_EVENTS, get_event_name, TRUE, TRUE},
       {EXPAND_AUGROUP, get_augroup_name, TRUE, TRUE},
       {EXPAND_CSCOPE, get_cscope_name, TRUE, TRUE},
+      {EXPAND_SIGN, get_sign_name, TRUE, TRUE},
       {EXPAND_PROFILE, get_profile_name, TRUE, TRUE},
 #ifdef HAVE_WORKING_LIBINTL
       {EXPAND_LANGUAGE, get_lang_arg, TRUE, FALSE},

test/functional/ui/wildmode_spec.lua

@@ -0,0 +1,32 @@
+local helpers = require('test.functional.helpers')
+local Screen = require('test.functional.ui.screen')
+local clear, feed, execute = helpers.clear, helpers.feed, helpers.execute
+
+describe("'wildmode'", function()
+  local screen
+
+  before_each(function()
+    clear()
+    screen = Screen.new(25, 5)
+    screen:attach()
+  end)
+
+  after_each(function()
+    screen:detach()
+  end)
+
+  describe("'wildmenu'", function()
+    it(':sign <tab> shows wildmenu completions', function()
+      execute('set wildmode')
+      execute('set wildmenu')
+      feed(':sign <tab>')
+      screen:expect([[
+                                 |
+        ~                        |
+        ~                        |
+        define  jump  list  >    |
+        :sign define^            |
+      ]])
+    end)
+  end)
+end)