Distinguish section mutations from item mutations

[ivopintodasilva]

Hello 👋

On the original implementation of FlexibleDiff we are considering a section mutation happens when:

1. A section's metadata has changed;
2. The items of the sections have changed/moved.

I've forked the library and have been using a slightly different approach where the Changeset only reveals a section mutation when the actual section's metadata has changed, disregarding any changes on the section's items for this purpose.

In my use case, this gives me a direct correlation between the changeset and the updates that I need to perform on a given collection view:

• I can update a section header only when a section's metadata has changed;
• When only items have changed I don't need to "refresh" the whole section.

What do you think about this approach?

Thanks for the great work! 😃

[andersio]

will need to be released as a major version

[andersio]

FlexibleDiff/FlexibleDiff/SectionedChangeset.swift

Lines 31 to 33 in fe1cd9f

	/// - precondition: Offsets in `sections.mutations` and `sections.moves` must have a
	/// corresponding entry in `mutatedSections` if they represent a
	/// mutation.

The precondition here is no longer valid, so it will need to be updated.

Since this has to be released as a API breaking change, I wonder if it is worth dropping SectionedChangeset.sections, and re-introduce the index sets to be top-level field of SectionedChangeset. This then allows us to rename sections.mutations to metadataMutated to make a strong distinction vs mutatedSections (maybe rename to itemMutatedSections).

[p4checo]

Bumping this 😇

@andersio are you still waiting for changes, or can this work get merged and a new release cut? Thanks! 🙏🏼