Implemented backup files for the configuration file

Currently, up to 10 backups are kept.
"klayoutrc.1" is the most recent backup, "klayoutrc." the
second most recent etc.

src/lay/lay/gsiDeclLayApplication.cc

@@ -164,12 +164,17 @@ static gsi::Methods application_methods ()
     //  TODO: basically this method belongs to Dispatcher (aka MainWindow).
     //  There is separate declaration for Dispatcher which we have to synchronize
     //  with this method.
-    method<C, bool, const std::string &> ("write_config", &C::write_config, gsi::arg ("file_name"),
+    method<C, bool, const std::string &, int> ("write_config", &C::write_config, gsi::arg ("file_name"), gsi::arg ("keep_backups", 0),
       "@brief Writes configuration to a file\n"
       "@return A value indicating whether the operation was successful\n"
       "\n"
       "If the configuration file cannot be written, \n"
       "is returned but no exception is thrown.\n"
+      "\n"
+      "@param file_name The path to write the config file to.\n"
+      "@param keep_backups The number of backups to keep (0 for 'no backups').\n"
+      "\n"
+      "The 'keep_backups' option was introduced in version 0.30.7.\n"
     ) +
     //  TODO: basically this method belongs to Dispatcher (aka MainWindow).
     //  There is separate declaration for Dispatcher which we have to synchronize

src/lay/lay/gsiDeclLayMainWindow.cc

@@ -202,9 +202,9 @@ static void clear_config (lay::MainWindow *mw)
   mw->dispatcher ()->clear_config ();
 }
 
-static bool write_config (lay::MainWindow *mw, const std::string &config_file)
+static bool write_config (lay::MainWindow *mw, const std::string &config_file, int keep_backups)
 {
-  return mw->dispatcher ()->write_config (config_file);
+  return mw->dispatcher ()->write_config (config_file, keep_backups);
 }
 
 static bool read_config (lay::MainWindow *mw, const std::string &config_file)
@@ -348,7 +348,7 @@ Class<lay::MainWindow> decl_MainWindow (QT_EXTERNAL_BASE (QMainWindow) "lay", "M
     "\n"
     "This method has been introduced in version 0.27.\n"
   ) +
-  method_ext ("write_config", &write_config, gsi::arg ("file_name"),
+  method_ext ("write_config", &write_config, gsi::arg ("file_name"), gsi::arg ("keep_backups", 0),
     "@brief Writes configuration to a file\n"
     "This method is provided for using MainWindow without an Application object. "
     "It's a convience method which is equivalent to 'dispatcher().write_config(...)'. See \\Dispatcher#write_config for details.\n"

src/lay/lay/layApplication.cc

@@ -992,6 +992,8 @@ ApplicationBase::exit (int result)
   ::exit (result);
 }
 
+const int number_of_config_file_backups = 10;
+
 void 
 ApplicationBase::finish ()
 {
@@ -1001,7 +1003,7 @@ ApplicationBase::finish ()
       if (tl::verbosity () >= 20) {
         tl::info << tl::to_string (QObject::tr ("Updating configuration file ")) << m_config_file_to_write;
       }
-      dispatcher ()->write_config (m_config_file_to_write);
+      dispatcher ()->write_config (m_config_file_to_write, number_of_config_file_backups);
     }
     if (! m_config_file_to_delete.empty () && m_config_file_to_delete != m_config_file_to_write) {
       if (tl::verbosity () >= 20) {
@@ -1419,9 +1421,9 @@ ApplicationBase::process_events_impl (QEventLoop::ProcessEventsFlags /*flags*/,
 }
 
 bool 
-ApplicationBase::write_config (const std::string &config_file)
+ApplicationBase::write_config (const std::string &config_file, int keep_backups)
 {
-  return dispatcher () ? dispatcher ()->write_config (config_file) : 0;
+  return dispatcher () ? dispatcher ()->write_config (config_file, keep_backups) : 0;
 }
 
 void 

src/lay/lay/layApplication.h

@@ -183,8 +183,11 @@ public:
    *
    *  If the configuration file cannot be written, false
    *  is returned but no exception is thrown.
+   *
+   *  "keep_backups" controls how many backups are kept for
+   *  the configuration file.
    */
-  bool write_config (const std::string &config_file);
+  bool write_config (const std::string &config_file, int keep_backups = 0);
 
   /**
    *  @brief Read the configuration from a file

src/laybasic/laybasic/gsiDeclLayDispatcher.cc

@@ -71,12 +71,17 @@ Class<lay::Dispatcher> decl_Dispatcher ("lay", "Dispatcher",
     "\n"
     "@return The instance\n"
   ) +
-  method ("write_config", &lay::Dispatcher::write_config, gsi::arg ("file_name"),
+  method ("write_config", &lay::Dispatcher::write_config, gsi::arg ("file_name"), gsi::arg ("keep_backups", 0),
     "@brief Writes configuration to a file\n"
     "@return A value indicating whether the operation was successful\n"
     "\n"
     "If the configuration file cannot be written, false \n"
     "is returned but no exception is thrown.\n"
+    "\n"
+    "@param file_name The path to write the config file to.\n"
+    "@param keep_backups The number of backups to keep (0 for 'no backups').\n"
+    "\n"
+    "The 'keep_backups' option was introduced in version 0.30.7.\n"
   ) +
   method ("read_config", &lay::Dispatcher::read_config, gsi::arg ("file_name"),
     "@brief Reads the configuration from a file\n"

src/laybasic/laybasic/layDispatcher.cc

@@ -238,10 +238,10 @@ config_structure (const lay::Dispatcher *plugin)
 
 
 bool
-Dispatcher::write_config (const std::string &config_file)
+Dispatcher::write_config (const std::string &config_file, int keep_backups)
 {
   try {
-    tl::OutputStream os (config_file, tl::OutputStream::OM_Plain);
+    tl::OutputStream os (config_file, tl::OutputStream::OM_Plain, true, keep_backups);
     config_structure (this).write (os, *this);
     return true;
   } catch (...) {

src/laybasic/laybasic/layDispatcher.h

@@ -147,9 +147,12 @@ public:
    *  If the configuration file cannot be written, false
    *  is returned but no exception is thrown.
    *
+   *  "keep_backups" is the number of backup files kept.
+   *  By default, no backups are kept.
+   *
    *  @return false, if an error occurred.
    */
-  bool write_config (const std::string &config_file);
+  bool write_config (const std::string &config_file, int keep_backups = 0);
 
   /**
    *  @brief Read the configuration from a file