Merger

A rust proc macro to allow merging/updating structs. This crate provides a trait 'MergeFrom', and a derive macro of the same name. The behaviour currently mimics that of protobuf's MergeFrom:

• Scalar values get replaced.
• 'Repeated' values (Vec,String) append.
• Maps (BTreeMap,HashMap) recursively merge fields that exist in both, or insert.
• Enums are supported for unit variants or variants with 1 field. unit variants work like scalars (replaced), while variants with a field either merge the field (if same variant in both 'to' and 'from') or replace (if different variants in 'to' and 'from')

TODOs

• Add support for specifying custom merge function (for example if you'd like Vec to also replace).
• Add support for ignoring fields (useful if you have fields that should only be set explicitly).

Contributing

Yes please.