BB-585: Revisions should clearly mark removed entities

[akashgp09]

Problem

This PR Fixes: BB-585

Solution

• utilized entity dataId to mark a deleted entity.
• deleted entity should have parentAlias and existing entity should have defaultAlias

Before

After

Areas of Impact

• routes/revision.js
• diffFormatters/entity.js

[coveralls]

Coverage increased (+0.009%) to 60.919% when pulling 50204d2 on akashgp09:mark-removed-entity-revision into 0aea892 on bookbrainz:master.

[MonkeyDo]

This works well for the most part. Seems to display deleted entities correctly in all cases I checked.

I'm seeing a regression in the way merged entities are displayed though, showing the BBID of the entity they are merged into rather than their own BBID :
Compare this screenshot from bb.org:

… to this one running this PR locally:

A clue might lie in this comment in the deleted code in diffFormatters/entity.js :
For entities without data (deleted or merged), we use getEntityParentAlias instead which returns a JSON object

[MonkeyDo]

I think this is almost ready. Deleted entities are shown as expected, so that part seems solved.

However I believe that now a revision where we create a new entity will appear like the entity was deleted:

Screenshot from this revision mentioned in the BB-585 ticket: http://localhost:9099/revision/3212

[MonkeyDo]

Thanks for this good feature !
Now it will be a lot clearer when an entity has been deleted, even looking at its history.

I took the liberty to make the modifications I suggested on IRC; I added hover text for the strikethrough names and for the "new", "deleted" and "merged" badges to help avoid possible confusion.

Hovering on the strikethrough name:

Hovering on the "new" badge: