vim-patch:8.2.2231: when "--remote file" is used "file" is not reloaded

Problem:    When "--remote file" is used "file" is not reloaded.
Solution:   When a :drop command is used for a file that is already displayed
            in a window and it has not been changed, check if it needs to be
            reloaded. (closes vim/vim#7560)
e4862a0fe6

Remove unused "focus" parameter from "buf_check_timestamp()".
It was meant for removed GUI code.

src/nvim/buffer.c

@@ -1587,7 +1587,7 @@ void enter_buffer(buf_T *buf)
       need_fileinfo = true;             // display file info after redraw
     }
     // check if file changed
-    (void)buf_check_timestamp(curbuf, false);
+    (void)buf_check_timestamp(curbuf);
 
     curwin->w_topline = 1;
     curwin->w_topfill = 0;

src/nvim/diff.c

@@ -805,7 +805,7 @@ static void diff_try_update(diffio_T    *dio,
     for (idx_new = idx_orig; idx_new < DB_COUNT; idx_new++) {
       buf = curtab->tp_diffbuf[idx_new];
       if (buf_valid(buf)) {
-        buf_check_timestamp(buf, false);
+        buf_check_timestamp(buf);
       }
     }
   }

src/nvim/ex_cmds.c

@@ -2323,7 +2323,7 @@ int do_ecmd(
       // Existing memfile.
       oldbuf = true;
       set_bufref(&bufref, buf);
-      (void)buf_check_timestamp(buf, false);
+      (void)buf_check_timestamp(buf);
       // Check if autocommands made buffer invalid or changed the current
       // buffer.
       if (!bufref_valid(&bufref) || curbuf != old_curbuf.br_buf) {

src/nvim/ex_cmds2.c

@@ -3392,7 +3392,7 @@ void ex_checktime(exarg_T *eap)
   } else {
     buf = buflist_findnr((int)eap->line2);
     if (buf != NULL) {           // cannot happen?
-      (void)buf_check_timestamp(buf, false);
+      (void)buf_check_timestamp(buf);
     }
   }
   no_check_timestamps = save_no_check_timestamps;
@@ -3790,6 +3790,14 @@ void ex_drop(exarg_T   *eap)
       if (wp->w_buffer == buf) {
         goto_tabpage_win(tp, wp);
         curwin->w_arg_idx = 0;
+        if (!bufIsChanged(curbuf)) {
+          const int save_ar = curbuf->b_p_ar;
+
+          // reload the file if it is newer
+          curbuf->b_p_ar = 1;
+          buf_check_timestamp(curbuf);
+          curbuf->b_p_ar = save_ar;
+        }
         return;
       }
     }

src/nvim/fileio.c

@@ -4675,7 +4675,6 @@ check_timestamps(
 )
 {
   int didit = 0;
-  int n;
 
   /* Don't check timestamps while system() or another low-level function may
    * cause us to lose and gain focus. */
@@ -4703,7 +4702,7 @@ check_timestamps(
       if (buf->b_nwindows > 0) {
         bufref_T bufref;
         set_bufref(&bufref, buf);
-        n = buf_check_timestamp(buf, focus);
+        const int n = buf_check_timestamp(buf);
         if (didit < n) {
           didit = n;
         }
@@ -4773,11 +4772,7 @@ static int move_lines(buf_T *frombuf, buf_T *tobuf)
  * return 2 if a message has been displayed.
  * return 0 otherwise.
  */
-int
+int buf_check_timestamp(buf_T *buf)
-buf_check_timestamp(
-    buf_T *buf,
-    int focus               /* called for GUI focus event */
-)
   FUNC_ATTR_NONNULL_ALL
 {
   int retval = 0;

src/nvim/testdir/test_clientserver.vim

@@ -61,6 +61,15 @@ func Test_client_server()
 
   call assert_fails('call remote_send("XXX", ":let testvar = ''yes''\<CR>")', 'E241')
 
+  call writefile(['one'], 'Xclientfile')
+  let cmd = GetVimProg() .. ' --servername ' .. name .. ' --remote Xclientfile'
+  call system(cmd)
+  call WaitForAssert({-> assert_equal('Xclientfile', remote_expr(name, "bufname()", "", 2))})
+  call WaitForAssert({-> assert_equal('one', remote_expr(name, "getline(1)", "", 2))})
+  call writefile(['one', 'two'], 'Xclientfile')
+  call system(cmd)
+  call WaitForAssert({-> assert_equal('two', remote_expr(name, "getline(2)", "", 2))})
+
   " Expression evaluated locally.
   if v:servername == ''
     call remote_startserver('MYSELF')