patch 8.0.0319: insert mode completion does not respect 'backspace'

Problem:    Insert mode completion does not respect "start" in 'backspace'.
Solution:   Check whether backspace can go before where insert started.
            (Hirohito Higashi)

src/edit.c

@@ -3467,10 +3467,13 @@ ins_compl_bs(void)
     mb_ptr_back(line, p);
 
     /* Stop completion when the whole word was deleted.  For Omni completion
-     * allow the word to be deleted, we won't match everything. */
+     * allow the word to be deleted, we won't match everything.
+     * Respect the 'backspace' option. */
     if ((int)(p - line) - (int)compl_col < 0
 	    || ((int)(p - line) - (int)compl_col == 0
-		&& ctrl_x_mode != CTRL_X_OMNI) || ctrl_x_mode == CTRL_X_EVAL)
+		&& ctrl_x_mode != CTRL_X_OMNI) || ctrl_x_mode == CTRL_X_EVAL
+	    || (!can_bs(BS_START) && (int)(p - line) - (int)compl_col
+							- compl_length < 0))
 	return K_BS;
 
     /* Deleted more than what was used to find matches or didn't finish

src/testdir/test_popup.vim

@@ -511,4 +511,24 @@ func Test_completion_clear_candidate_list()
   bw!
 endfunc
 
+func Test_completion_respect_bs_option()
+  new
+  let li = ["aaa", "aaa12345", "aaaabcdef", "aaaABC"]
+
+  set bs=indent,eol
+  call setline(1, li)
+  1
+  call feedkeys("A\<C-X>\<C-N>\<C-P>\<BS>\<BS>\<BS>\<Esc>", "tx")
+  call assert_equal('aaa', getline(1))
+
+  %d
+  set bs=indent,eol,start
+  call setline(1, li)
+  1
+  call feedkeys("A\<C-X>\<C-N>\<C-P>\<BS>\<BS>\<BS>\<Esc>", "tx")
+  call assert_equal('', getline(1))
+
+  bw!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    319,
 /**/
     318,
 /**/