disable including 'mtime' in new torrents by default

docs/make_torrent.rst

@@ -217,7 +217,7 @@ The ``create_torrent`` class has the following synopsis::
 
 	struct create_torrent
 	{
-		enum { optimize = 1, merkle = 2 };
+		enum { optimize = 1, merkle = 2, modification_time = 4 };
 		create_torrent(file_storage& fs, int piece_size = 0, int pad_size_limit = -1, int flags = optimize);
 		create_torrent(torrent_info const& ti);
 
@@ -244,7 +244,7 @@ create_torrent()
 
 	::
 
-		enum { optimize = 1, merkle = 2 };
+		enum { optimize = 1, merkle = 2, modification_time = 4 };
 		create_torrent(file_storage& fs, int piece_size = 0, int pad_size_limit = -1, int flags = optimize);
 		create_torrent(torrent_info const& ti);
 
@@ -278,6 +278,14 @@ merkle
 	not grow with more pieces. When this option is specified, it is
 	recommended to have a fairly small piece size, say 64 kiB.
 
+modification_time
+	This will include the file modification time as part of the torrent.
+	This is not enabled by default, as it might cause problems when you
+	create a torrent from separate files with the same content, hoping to
+	yield the same info-hash. If the files have different modification times,
+	with this option enabled, you would get different info-hashes for the
+	files.
+
 generate()
 ----------
 

include/libtorrent/create_torrent.hpp

@@ -66,7 +66,7 @@ namespace libtorrent
 
 	struct TORRENT_EXPORT create_torrent
 	{
-		enum { optimize = 1, merkle = 2 };
+		enum { optimize = 1, merkle = 2, modification_time = 4 };
 
 		create_torrent(file_storage& fs, int piece_size = 0
 			, int pad_file_limit = -1, int flags = optimize);
@@ -139,6 +139,10 @@ namespace libtorrent
 
 		// if set to one, a merkle torrent will be generated
 		bool m_merkle_torrent:1;
+
+		// if set, include the 'mtime' modification time in the
+		// torrent file
+		bool m_include_mtime:1;
 	};
 
 	namespace detail

src/create_torrent.cpp

@@ -113,6 +113,7 @@ namespace libtorrent
 		, m_multifile(fs.num_files() > 1)
 		, m_private(false)
 		, m_merkle_torrent(flags & merkle)
+		, m_include_mtime(flags & modification_time)
 	{
 		TORRENT_ASSERT(fs.num_files() > 0);
 
@@ -278,7 +279,10 @@ namespace libtorrent
 
 		if (!m_multifile)
 		{
-			info["mtime"] = m_files.at(0).mtime;
+			if (m_include_mtime)
+			{
+				info["mtime"] = m_files.at(0).mtime;
+			}
 			info["length"] = m_files.at(0).size;
 			if (m_files.at(0).pad_file
 				|| m_files.at(0).hidden_attribute
@@ -311,7 +315,10 @@ namespace libtorrent
 				{
 					files.list().push_back(entry());
 					entry& file_e = files.list().back();
-					file_e["mtime"] = i->mtime; 
+					if (m_include_mtime)
+					{
+						file_e["mtime"] = i->mtime; 
+					}
 					file_e["length"] = i->size;
 					entry& path_e = file_e["path"];