vim-patch:8.0.1787: cannot insert the whole cursor line

Problem:    Cannot insert the whole cursor line.
Solution:   Make CTRL-R CTRL-L work. (Andy Massimino, closes vim/vim#2857)
e2c8d83926

src/nvim/ex_getln.c

@@ -3295,8 +3295,10 @@ static bool cmdline_paste(int regname, bool literally, bool remcr)
   /* check for valid regname; also accept special characters for CTRL-R in
    * the command line */
   if (regname != Ctrl_F && regname != Ctrl_P && regname != Ctrl_W
-      && regname != Ctrl_A && !valid_yank_reg(regname, false))
+      && regname != Ctrl_A && regname != Ctrl_L
+      && !valid_yank_reg(regname, false)) {
     return FAIL;
+  }
 
   /* A register containing CTRL-R can cause an endless loop.  Allow using
    * CTRL-C to break the loop. */

src/nvim/ops.c

@@ -1257,6 +1257,14 @@ int get_spec_reg(
     *allocated = TRUE;
     return TRUE;
 
+  case Ctrl_L:                  // Line under cursor
+    if (!errmsg) {
+      return false;
+    }
+
+    *argp = ml_get_buf(curwin->w_buffer, curwin->w_cursor.lnum, false);
+    return true;
+
   case '_':                     /* black hole: always empty */
     *argp = (char_u *)"";
     return TRUE;

src/nvim/testdir/test_cmdline.vim

@@ -321,6 +321,9 @@ func Test_paste_in_cmdline()
   call feedkeys("ft:aaa \<C-R>\<C-F> bbb\<C-B>\"\<CR>", 'tx')
   call assert_equal('"aaa /tmp/some bbb', @:)
 
+  call feedkeys(":aaa \<C-R>\<C-L> bbb\<C-B>\"\<CR>", 'tx')
+  call assert_equal('"aaa '.getline(1).' bbb', @:)
+
   set incsearch
   call feedkeys("fy:aaa veryl\<C-R>\<C-W> bbb\<C-B>\"\<CR>", 'tx')
   call assert_equal('"aaa verylongword bbb', @:)