Implement --backup-dir - fixes #98

The parameter of backup-dir specifies a remote that all deleted or
overwritten files will be copied to.

fs/config.go

@@ -86,6 +86,7 @@ var (
 	ignoreSize      = BoolP("ignore-size", "", false, "Ignore size when skipping use mod-time or checksum.")
 	noTraverse      = BoolP("no-traverse", "", false, "Don't traverse destination file system on copy.")
 	noUpdateModTime = BoolP("no-update-modtime", "", false, "Don't update destination mod-time if files identical.")
+	backupDir       = StringP("backup-dir", "", "", "Make backups into hierarchy based in DIR.")
 	bwLimit         BwTimetable
 
 	// Key to use for password en/decryption.
@@ -209,6 +210,7 @@ type ConfigInfo struct {
 	NoTraverse         bool
 	NoUpdateModTime    bool
 	DataRateUnit       string
+	BackupDir          string
 }
 
 // Find the config directory
@@ -260,6 +262,7 @@ func LoadConfig() {
 	Config.IgnoreSize = *ignoreSize
 	Config.NoTraverse = *noTraverse
 	Config.NoUpdateModTime = *noUpdateModTime
+	Config.BackupDir = *backupDir
 
 	ConfigPath = *configFile