Operating system

MacOS Montery 12.5.1

Helmfile Version

helmfile version v0.145.2

Helm Version

version.BuildInfo{Version:"v3.9.3", GitCommit:"414ff28d4029ae8c8b05d62aa06c7fe3dee2bc58", GitTreeState:"clean", GoVersion:"go1.19"}

Bug description

See: roboll/helmfile#657

This fails with "already set in map"

Example helmfile.yaml

templates:
  default: &default
    labels:
      sync: everyday
charts:
  - name: test
    <<: *default
    chart: test
    labels:
      sync: thur

Error message you've seen (if any)

already set in map

Steps to reproduce

override an existing value in a yaml file

Relevant discussion

roboll/helmfile#657