Activity feed: View version snapshots alongside versions (PoC)

[chillu]

Overview

We are creating a datamodel to capture how changes affect objects in an ownership graph through the https://github.com/open-sausages/silverstripe-versioned-snapshots experimental module.

This card is aimed at creating a PoC implementation. The full implementation for versioned-admin is at #114

Acceptance Criteria

• For objects supported by the existing version history viewer, I can view snapshots which involved this object
• I can view snapshots alongside their versioned entries, through a combined sort
• Both types (versions and snapshots) are sorted as if they were one list
• I can paginate both types (versions and snapshots) as if they were one list
• The viewer continues to support 100k+ version entries
• If the snapshot was created as part of an explicit version for the object, it doesn't show as a duplicate
• Version snapshots show the version number of the object they're associated with
• I am prevented from selecting snapshots in comparisons, because it doesn't make sense until we show an activity feed alongside comparison view
• I can view the details of a snapshot by viewing the version of the object which the snapshot was based on.
• The snapshot detail has a list of changes contained in this snapshot (see activity feed)
• I can revert to a snapshot (based on the date the snapshot was taken)
• For pages: I can preview the object (base on the date the snapshot was taken)

Notes

• We'll need to limit the number of snapshot items to show (particularly when comparing versions with may edits between them, and large ownership structures). We're not implementing pagination of activity feed just yet

[clarkepaul]

Right now I'm struggling to imagine the UI for this so that it makes sense, a few questions:

Does each save/publish of a related item create a snapshot or only when a person chooses to take a snapshot?

When comparing versions and snapshots, it shows all snapshot entries which happened between these two versions

Does this apply to a snapshot and a really old version, or just with the version the snapshot is directly associated to? otherwise there could be a lot of changes.

It feels like a snapshot is more time based which is a true representation of whats happened, where as our version relation model doesn't seem to provide the user a good view for a certain time. Shouldn't we base history on time as opposed to version? @chillu

[chillu]

@unclecheese Removing this from milestone, with the assumption that we can do any required core modules in a 4.4.1

[chillu]

After talking to Aaron, we removed these two ACs:

I can compare versions and snapshots, which chooses the version which the snapshot was based on
When comparing versions and snapshots, it shows all snapshot entries which happened between these two versions

[chillu]

I've duplicated this card to reflect that we're only creating a private PoC for one bespoke project here. The full implementation will be handled through #114

[unclecheese]

Closing, as all ACs have been met. Last bit is getting this delivered to our project, which @ScopeyNZ is carrying out in a flurry of separate PRs and review directly to the snaspshot-admin module.