patch 9.0.1299: change for triggering incsearch not sufficiently tested

Problem:    Change for triggering incsearch not sufficiently tested.
Solution:   Add a test case.  Simplify the code. (closes #11971)

src/ex_getln.c

@@ -1253,9 +1253,9 @@ cmdline_insert_reg(int *gotesc UNUSED)
     // remove the double quote
     redrawcmd();
 
-    // The text has been stuffed, the command line didn't change yet, but it
-    // will change soon.  The caller must take care of it.
-    return literally ? CMDLINE_NOT_CHANGED : CMDLINE_CHANGED;
+    // With "literally": the command line has already changed.
+    // Else: the text has been stuffed, but the command line didn't change yet.
+    return literally ? CMDLINE_CHANGED : CMDLINE_NOT_CHANGED;
 }
 
 /*
@@ -2086,10 +2086,8 @@ getcmdline_int(
 		res = cmdline_insert_reg(&gotesc);
 		if (res == GOTO_NORMAL_MODE)
 		    goto returncmd;
-#ifdef FEAT_SEARCH_EXTRA
-		if (res == CMDLINE_NOT_CHANGED)
-		    is_state.incsearch_postponed = TRUE;
-#endif
+		if (res == CMDLINE_CHANGED)
+		    goto cmdline_changed;
 		goto cmdline_not_changed;
 
 	case Ctrl_D:

src/testdir/test_autocmd.vim

@@ -1909,17 +1909,15 @@ func Test_Cmdline()
   call assert_equal(':', g:entered)
   au! CmdlineChanged
 
+  autocmd CmdlineChanged : let g:log += [getcmdline()]
+
   let g:log = []
   cnoremap <F1> <Cmd>call setcmdline('ls')<CR>
-  autocmd CmdlineChanged : let g:log += [getcmdline()]
   call feedkeys(":\<F1>", 'xt')
   call assert_equal(['ls'], g:log)
-  unlet g:log
-  au! CmdlineChanged
   cunmap <F1>
 
   let g:log = []
-  autocmd CmdlineChanged : let g:log += [getcmdline()]
   call feedkeys(":sign \<Tab>\<Tab>\<C-N>\<C-P>\<S-Tab>\<S-Tab>\<Esc>", 'xt')
   call assert_equal([
         \ 's',
@@ -1950,6 +1948,22 @@ func Test_Cmdline()
         \ 'sign unplace',
         \ ], g:log)
   set wildmenu& wildoptions&
+
+  let g:log = []
+  let @r = 'abc'
+  call feedkeys(":0\<C-R>r1\<C-R>\<C-O>r2\<C-R>\<C-R>r3\<Esc>", 'xt')
+  call assert_equal([
+        \ '0',
+        \ '0a',
+        \ '0ab',
+        \ '0abc',
+        \ '0abc1',
+        \ '0abc1abc',
+        \ '0abc1abc2',
+        \ '0abc1abc2abc',
+        \ '0abc1abc2abc3',
+        \ ], g:log)
+
   unlet g:log
   au! CmdlineChanged
 

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1299,
 /**/
     1298,
 /**/