clarify auditFile documentation

README.md

@@ -28,7 +28,7 @@ The DailyRotateFile transport can rotate files by minute, hour, day, month, year
 * **maxSize:** Maximum size of the file after which it will rotate. This can be a number of bytes, or units of kb, mb, and gb. If using the units, add 'k', 'm', or 'g' as the suffix. The units need to directly follow the number. (default: null)
 * **maxFiles:** Maximum number of logs to keep. If not set, no logs will be removed. This can be a number of files or number of days. If using days, add 'd' as the suffix. It uses auditFile to keep track of the log files in a json format. It won't delete any file not contained in it. It can be a number of files or number of days (default: null)
 * **options:** An object resembling https://nodejs.org/api/fs.html#fs_fs_createwritestream_path_options indicating additional options that should be passed to the file stream. (default: `{ flags: 'a' }`)
-* **auditFile**: A string representing the name of the audit file. This can be used to override the default filename which is generated by computing a hash of the options object. (default: '.<optionsHash>.json')
+* **auditFile**: A string representing the path of the audit file, passed directly to [file-stream-rotator](https://github.com/rogerc/file-stream-rotator/) as `audit_file`.  If not specified, a file name is generated that includes a hash computed from the options object, and uses the `dirname` option value as the directory. (default: `<dirname>/.<optionsHash>-audit.json`)
 * **utc**: Use UTC time for date in filename. (default: false)
 * **extension**: File extension to be appended to the filename. (default: '')
 * **createSymlink**: Create a tailable symlink to the current active log file. (default: false)