This feature offers two possibility:

• storing the filerev summary to a file
• stripping the src/dest paths of the filerev summary

Therefore two option parameters are supported:

• summaryFilePath
• stripPath

summaryFilePath defines the path, where the filerev summary should be stored.
stripPath can be used to strip the src/dest summary paths. The value can either be a string, or an object with the properties src and dest. If only a string is passed, this string is removed from all src and dest paths. If an object is passed, src and dest paths get treated individually.

Example:

options: {
      algorithm: 'md5',
      length: 8,
      summaryFilePath: './tasks/filerevsummary.json',
      stripPath: {
        src: 'assets',
        dest: '.tmp/public'
      }
    },

My use-case:
I implemented this feature because I needed the filerev summary in a view helper to provide the hashed source path when a view gets loaded. Therefore the summary had to be stored somewhere locally.