patch 8.2.0019: cannot number of lines of another buffer

Problem:    Cannot number of lines of another buffer.
Solution:   Add "linecount" to getbufinfo(). (Yasuhiro Matsumoto,
            closes #5370)

runtime/doc/eval.txt

@@ -4796,6 +4796,8 @@ getbufinfo([{dict}])
 					{only with the |+viminfo| feature}
 			listed		TRUE if the buffer is listed.
 			lnum		current line number in buffer.
+			linecount	number of lines in the buffer (only
+					valid when loaded)
 			loaded		TRUE if the buffer is loaded.
 			name		full path to the file in the buffer.
 			signs		list of signs placed in the buffer.

src/evalbuffer.c

@@ -545,6 +545,7 @@ get_buffer_info(buf_T *buf)
     dict_add_string(dict, "name", buf->b_ffname);
     dict_add_number(dict, "lnum", buf == curbuf ? curwin->w_cursor.lnum
 						     : buflist_findlnum(buf));
+    dict_add_number(dict, "linecount", buf->b_ml.ml_line_count);
     dict_add_number(dict, "loaded", buf->b_ml.ml_mfp != NULL);
     dict_add_number(dict, "listed", buf->b_p_bl);
     dict_add_number(dict, "changed", bufIsChanged(buf));

src/testdir/test_bufwintabinfo.vim

@@ -154,3 +154,13 @@ function Test_getbufinfo_lastused()
   call assert_equal(getbufinfo('Xtestfile2')[0].lastused, 7654321)
   call test_settime(0)
 endfunc
+
+func Test_getbufinfo_lines()
+  new Xfoo
+  call setline(1, ['a', 'bc', 'd'])
+  let bn = bufnr('%')
+  hide
+  call assert_equal(3, getbufinfo(bn)[0]["linecount"])
+  edit Xfoo
+  bw!
+endfunc

src/version.c

@@ -742,6 +742,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    19,
 /**/
     18,
 /**/