Is it possible to substitute (without the use of external tools like envsubst) values in an environment file used in docker-compose (using env_file) with values on a .env file in the folder?
Say I have this .env file:
REGISTRY=something
TAG=something-else
Now in my docker-compose.yml I can have:
# ...
my_service:
environment:
- USE_IMAGE:${REGISTRY}/my_image:${TAG}
# ...
What I'd like is having a different environment file (say, myservice.env), like this:
USE_IMAGE=${REGISTRY}/my_image:${TAG}
And use it on the compose file like:
# ...
my_service:
env_file:
- myservice.env
# ...
However by default, docker-compose (which is the one reading the .env file) doesn't seem to be substituting anything on the other files and I get the literal value.
Is there a way to do this without requiring to have a "rendered" file, directly with docker compose?
I understand I could make a script to pre-process those files using envsubst or something similar, but I'm trying to find a solution without that
