patch 8.2.2166: auto format doesn't work when deleting text

Problem:    Auto format doesn't work when deleting text.
Solution:   Make "x" trigger auto format. (closes #7504)
diff --git a/src/ops.c b/src/ops.c
index b83394e..743bdd4 100644
--- a/src/ops.c
+++ b/src/ops.c
@@ -938,6 +938,7 @@
 	    curwin->w_cursor = curpos;	// restore curwin->w_cursor
 	    (void)do_join(2, FALSE, FALSE, FALSE, FALSE);
 	}
+	auto_format(FALSE, TRUE);
     }
 
     msgmore(curbuf->b_ml.ml_line_count - old_lcount);
diff --git a/src/testdir/test_textformat.vim b/src/testdir/test_textformat.vim
index a91c3da..eac1c19 100644
--- a/src/testdir/test_textformat.vim
+++ b/src/testdir/test_textformat.vim
@@ -934,6 +934,18 @@
   call assert_equal('g uu uu ', getline(1)[-8:])
   call assert_equal(['uu. foo'], getline(2, '$'))
 
+  " using backspace or "x" triggers reformat
+  call setline(1, ['1 2 3 4 5 ', '6 7 8 9'])
+  set tw=10
+  set fo=taw
+  set bs=indent,eol,start
+  exe "normal 1G4la\<BS>\<BS>\<Esc>"
+  call assert_equal(['1 2 4 5 6 ', '7 8 9'], getline(1, 2))
+  exe "normal f4xx"
+  call assert_equal(['1 2 5 6 7 ', '8 9'], getline(1, 2))
+
+  set tw=0
+  set fo&
   %bw!
 endfunc
 
diff --git a/src/version.c b/src/version.c
index fe06be0..ac6fb12 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2166,
+/**/
     2165,
 /**/
     2164,