add flag for initializing m_need_save_resume_data when adding torrent

include/libtorrent/add_torrent_params.hpp

@@ -271,9 +271,16 @@ namespace libtorrent
 			// list of web seeds used by the torrent.
 			flag_override_web_seeds = 0x10000,
 
+			// if this flag is set (which it is by default) the torrent will be
+			// considered needing to save its resume data immediately as it's
+			// added. New torrents that don't have any resume data should do that.
+			// This flag is cleared by a successful call to read_resume_data()
+			flag_need_save_resume = 0x20000,
+
 			// internal
 			default_flags = flag_pinned | flag_update_subscribe
 				| flag_auto_managed | flag_paused | flag_apply_ip_filter
+				| flag_need_save_resume
 #ifndef TORRENT_NO_DEPRECATE
 				| flag_merge_resume_http_seeds
 				| flag_merge_resume_trackers

src/read_resume_data.cpp

@@ -327,6 +327,8 @@ namespace libtorrent
 			}
 		}
 
+		ret.flags &= ~add_torrent_params::flag_need_save_resume;
+
 		return ret;
 	}
 

src/torrent.cpp

@@ -244,7 +244,7 @@ namespace libtorrent
 		, m_resolve_countries(false)
 #endif
 #endif
-		, m_need_save_resume_data(true)
+		, m_need_save_resume_data(p.flags & add_torrent_params::flag_need_save_resume)
 		, m_seeding_time(0)
 		, m_max_uploads((1<<24)-1)
 		, m_save_resume_flags(0)
@@ -290,12 +290,6 @@ namespace libtorrent
 
 		inc_stats_counter(counters::num_loaded_torrents);
 
-		// if there is resume data already, we don't need to trigger the initial save
-		// resume data
-//TODO: 4 maybe m_need_save_resume_data should be another flag in add_torrent_params
-		if (!p.have_pieces.empty() /* && (p.flags & add_torrent_params::flag_override_resume_data) == 0 */ )
-			m_need_save_resume_data = false;
-
 #if TORRENT_USE_UNC_PATHS
 		m_save_path = canonicalize_path(m_save_path);
 #endif