patch 8.1.0969: message written during startup is truncated

Problem:    Message written during startup is truncated.
Solution:   Restore message after truncating. (closes 3969)

src/message.c

@@ -2627,12 +2627,19 @@ msg_puts_printf(char_u *str, int maxlen)
 
     if (*p != NUL && !(silent_mode && p_verbose == 0))
     {
+	int c = -1;
+
 	if (maxlen > 0 && STRLEN(p) > (size_t)maxlen)
+	{
+	    c = p[maxlen];
 	    p[maxlen] = 0;
+	}
 	if (info_message)
 	    mch_msg((char *)p);
 	else
 	    mch_errmsg((char *)p);
+	if (c != -1)
+	    p[maxlen] = c;
     }
 
     msg_didout = TRUE;	    // assume that line is not empty

src/testdir/test_startup.vim

@@ -537,3 +537,13 @@ func Test_zzz_startinsert()
   endif
   call delete('Xtestout')
 endfunc
+
+func Test_issue_3969()
+  if has('gui_running')
+    " Can't catch the output of gvim.
+    return
+  endif
+  " Check that message is not truncated.
+  let out = system(GetVimCommand() . ' -es -X -V1 -c "echon ''hello''" -cq')
+  call assert_equal('hello', out)
+endfunc

src/version.c

@@ -779,6 +779,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    969,
 /**/
     968,
 /**/