vim-patch:8.2.1844: using "q" at the more prompt doesn't stop a long message

Problem:    Using "q" at the more prompt doesn't stop a long message.
Solution:   Check for "got_int". (closes vim/vim#7122)
3d30af8783

Cherry-pick file name change from patch 8.2.2112.

src/nvim/message.c

@@ -1486,6 +1486,10 @@ int msg_outtrans_len_attr(const char_u *msgstr, int len, int attr)
   char_u *s;
   int mb_l;
   int c;
+  int save_got_int = got_int;
+
+  // Only quit when got_int was set in here.
+  got_int = false;
 
   // if MSG_HIST flag set, add message to history
   if (attr & MSG_HIST) {
@@ -1503,7 +1507,7 @@ int msg_outtrans_len_attr(const char_u *msgstr, int len, int attr)
    * Go over the string.  Special characters are translated and printed.
    * Normal characters are printed several at a time.
    */
-  while (--len >= 0) {
+  while (--len >= 0 && !got_int) {
     // Don't include composing chars after the end.
     mb_l = utfc_ptr2len_len((char_u *)str, len + 1);
     if (mb_l > 1) {
@@ -1542,11 +1546,13 @@ int msg_outtrans_len_attr(const char_u *msgstr, int len, int attr)
     }
   }
 
-  if (str > plain_start) {
+  if (str > plain_start && !got_int) {
     // Print the printable chars at the end.
     msg_puts_attr_len(plain_start, str - plain_start, attr);
   }
 
+  got_int |= save_got_int;
+
   return retval;
 }
 

src/nvim/testdir/test_messages.vim

@@ -2,6 +2,9 @@
 
 source check.vim
 source shared.vim
+source term_util.vim
+source view_util.vim
+source screendump.vim
 
 func Test_messages()
   let oldmore = &more
@@ -109,6 +112,22 @@ func Test_echospace()
   set ruler& showcmd&
 endfunc
 
+func Test_quit_long_message()
+  CheckScreendump
+
+  let content =<< trim END
+    echom range(9999)->join("\x01")
+  END
+  call writefile(content, 'Xtest_quit_message')
+  let buf = RunVimInTerminal('-S Xtest_quit_message', #{rows: 6})
+  call term_sendkeys(buf, "q")
+  call VerifyScreenDump(buf, 'Test_quit_long_message', {})
+
+  " clean up
+  call StopVimInTerminal(buf)
+  call delete('Xtest_quit_message')
+endfunc
+
 " this was missing a terminating NUL
 func Test_echo_string_partial()
   function CountSpaces()