Add isUpdate filter to GetUpdates in GetGroupTangle

[Powersource]

See comments in this code. They used to be there in tribes1, when bringing it here i commented it out because the crut code was pretty opaque.

function GetUpdates(ssb) {
  const { seekKey } = require('bipf')
  //const { spec } = crut
  //const isUpdate = (msg) =>
  //  crut.isUpdate(getCanonicalContent(msg, spec.getTransformation))
  const B_TANGLE = Buffer.from('group')

  function tangleRoot(value) {
    return ssb.db.operators.equal(seekTangleRoot, value, {
      indexType: `value.content.tangles.group.root`,
    })
  }
  function seekTangleRoot(buffer) {
    let p = 0 // note you pass in p!
    p = seekKey(buffer, p, B_VALUE)
    if (p < 0) return
    p = seekKey(buffer, p, B_CONTENT)
    if (p < 0) return
    p = seekKey(buffer, p, B_TANGLES)
    if (p < 0) return
    p = seekKey(buffer, p, B_TANGLE)
    if (p < 0) return
    return seekKey(buffer, p, B_ROOT)
  }

  return function getUpdates(id, cb) {
    const { where, and, toPullStream } = ssb.db.operators
    pull(
      ssb.db.query(where(and(tangleRoot(id))), toPullStream()),
      //TODO: do we want this?
      //pull.filter(isUpdate),
      pull.collect(cb)
    )
  }
}

[Powersource]

cc @mixmix what magic is supposed to happen here?

[Powersource]

ah i guess this is a schema of some kind. to verify that all the needed fields are in the msg, like the tangles.

should check if this is actually needed anymore or if we check in other places.

should also be enough with a simple function in case we're just checking the tangle object, instead of a whole schema

[mixmix]

yeah just checking the tangles[tangle].root and tangles[tangle].previous are both there are and are the right shape an all....
Because we're about to start calculating things with them. 🤷