[FEATURE REQUEST] Implement poco run

[hron84]

It would be nice if poco would allow override a specified command to run in a service.

Real-world example is debugging a docker container. Currently - since Poco makes possible to collect environment variables from several files, there is no easy way to run and override command in the docker-compose command section.

I want similar functionality how docker-compose run -f docker/dc-shiwa.yml shiwa bash -l could work, but with the full support of substituting environment variables from the corresponding files.

CLI interface could be poco run PLAN CONTAINER command [args]

[sarkiroka]

one of poco's main functions is to do the complicated docker-compose commands for you. if you want to do this manually, it loses its meaning. in that case you can use your compiled command directly from shell

[hron84]

Exactly. However, poco is a generic tool, and sometimes we need to run for example one-shot maintenance tasks or generating reports with the exactly same environment and setting that is used by the application.

For example, imagine a Ruby on Rails application, which has some built-in tasks for maintaining database or generated statics. It is as simple as running rake db:migrate or rake assets:cleanup, but these commands need the environment variables from the docker config.

If I use a 3 container setup (db, redis, app) and I want to run these maintenance tasks, with poco I can run

poco run myapp rake db:migrate

while, without poco, I have to do similar to this:

docker compose run -f docker/dc-db.yml -f docker/dc-redis.yml -f docker/dc-app.yml --env ??? run 'rake db:migrate'

Where the correct environment inclusion can be even more difficult, if I normally rely on poco to load environment files instead of loading them with docker-compose YAMLs.