Support for supplying index settings on restore #1362

[robertlyson]

PR for #1362 issue.

For IndexSettings property on IRrestoreDescriptor I reused IUpdateSettingsRequest, but I'm not sure if this name fits in this context. Way how we can combine RestoreDescriptor with UpdateSettingsDescriptor is really nice.

Moreover, I've extracted all setting names to separate class. Avoiding googling for each plain index setting is really convenient.

Any thoughts? Let me know.
Thanks.

[Mpdreamz]

Love moving this out of the attributes 👍 suggestion on different name UpdatableSettings

[robertlyson]

@Mpdreamz much more better name 👍 . Maybe we should split this class into three? UpdatableSettings, UnmodifiableSettings and UnremovableSettings? https://github.com/elastic/elasticsearch/blob/master/src/main/java/org/elasticsearch/snapshots/RestoreService.java#L92-105

[Mpdreamz]

I don't see any settings in SettingsNames that are not Updatable though, maybe I need another coffee 😄

Where would we use Unmodifiable and Unremovable ?

[robertlyson]

Yeah, that's true, looks like I need second coffee :)
I'll change name to UpdatableSettings later on.

[Mpdreamz]

PR looks awesome as usual @robertlyson 👍 left a small comment.

[robertlyson]

Thanks for review. I've pushed change.

[Mpdreamz]

ty @robertlyson !