I have this values.yaml in my chart:

appConfig:
  spring:
    datasource: 
     ...
    cloud:
     ...

I want to extend these default values while installing/upgrading the release of this chart with another file src/application.yaml.

src/application.yaml

spring:
  datasource:
     ...

This is easy if the root object of this application.yaml is the same as values.yaml ( I mean "appConfig" by the root object).

In that case helm install -f src/application.yaml will be enough.

However, src/application.yaml must be merged with appConfig object.

I tried --set-file option as following:

helm install --set-file appConfig=src/application.yaml

Unfortunately, this option --set-file does not extend the object appConfig, instead, it totally override it.