Output a "flat" YAML

[debuglevel]

Please describe your feature request.
Create an output with the full path of each key instead of the usual hierarchical YAML syntax. I don't know whether this would actually be a valid YAML, but it would be nice to be used for further processing.

Describe the solution you'd like
Example given:

animals:
  dogs: 3
  cats: 5

would convert it to

animals.dogs: 3
animals.cats: 3

This would be useful for further processing, e.g. creating environment variables like often used with for Docker:

cat settings.yml | yq eval flatten-my-stuff | ./some-bash-script.sh

ANIMALS_DOG=3
ANIMALS_CATS=5

Describe alternatives you've considered
Probably could also be done with some Python.

[mikefarah]

.animals.[] | {(path | join(".")): .}

[mikefarah]

Also, see #699 for a more generic approach

[pascal-hofmann]

I need the reverse. Is there a way to unflatten a yaml file with yq?