Fix for errant SIGHUPs due to child fish shells messing with the term.

Fixes https://github.com/fish-shell/fish-shell/issues/1002

fish.cpp

@@ -389,7 +389,6 @@ int main(int argc, char **argv)
 
     set_main_thread();
     setup_fork_guards();
-    save_term_foreground_process_group();
 
     wsetlocale(LC_ALL, L"");
     is_interactive_session=1;
@@ -410,6 +409,12 @@ int main(int argc, char **argv)
         no_exec = 0;
     }
 
+    /* Only save (and therefore restore) the fg process group if we are interactive. See #197, #1002 */
+    if (is_interactive_session)
+    {
+        save_term_foreground_process_group();
+    }
+
     const struct config_paths_t paths = determine_config_directory_paths(argv[0]);
 
     proc_init();
@@ -511,6 +516,7 @@ int main(int argc, char **argv)
 
     proc_fire_event(L"PROCESS_EXIT", EVENT_EXIT, getpid(), res);
 
+    restore_term_mode();
     restore_term_foreground_process_group();
     history_destroy();
     proc_destroy();

reader.cpp

@@ -993,10 +993,18 @@ void reader_init()
 
 void reader_destroy()
 {
-    tcsetattr(0, TCSANOW, &terminal_mode_on_startup);
     pthread_key_delete(generation_count_key);
 }
 
+void restore_term_mode()
+{
+    // Restore the term mode if we own the terminal
+    // It's important we do this before restore_foreground_process_group, otherwise we won't think we own the terminal
+    if (getpid() == tcgetpgrp(STDIN_FILENO))
+    {
+        tcsetattr(STDIN_FILENO, TCSANOW, &terminal_mode_on_startup);
+    }
+}
 
 void reader_exit(int do_exit, int forced)
 {

reader.h

@@ -46,6 +46,9 @@ void reader_init();
 */
 void reader_destroy();
 
+/** Restore the term mode at startup */
+void restore_term_mode();
+
 /**
    Returns the filename of the file currently read
 */