code: function changeMeta (id, diff) {
      var key
      for (key in diff) {
        if (key === 'id' || key === 'added' || key === 'time') {
          throw new Error('Meta "' + key + '" is read-only')
        }
      }
  
      var emitter = this.emitter
      if (diff.reasons && diff.reasons.length === 0) {
        return this.store.remove(id).then(function (entry) {
          if (entry) {
            for (key in diff) entry[1][key] = diff[key]
            emitter.emit('clean', entry[0], entry[1])
          }
          return !!entry
        })
      } else {
        return this.store.changeMeta(id, diff)
      }
    }
docs: Change action metadata. You will remove action by setting `reasons: []`.
  
  @param {string} id Action ID.
  @param {object} diff Object with values to change in action metadata.
  
  @return {Promise} Promise with `true` if metadata was changed
  or `false` on unknown ID.
  
  @example
  await process(action)
  log.changeMeta(action, { status: 'processed' })