chore: drop support for pinning dokku dependencies

[ltalirz]

fix #130

Pinning the versions of dokku dependencies (herokuish, plugn,
sshcommand) was deprecated in 2021-02 [1] since it made updating dokku
tedious: users would have had to guess/look up what versions of the
dependencies were needed for the new dokku version.

The initial deprecation period was 6 months until July 2021; since this
has passed, the deprecated variables are now being removed.

[1] 0f8ce10

[ltalirz]

I'll hold off this PR until there's a review to answer the following open questions:

• Do we need code to warn users who use the deprecated variables?
• On second thought, I believe we may want to keep pinning (only) for the dokku package itself... not having a way to pin the dokku version makes it difficult to get reproducible builds across machines.
• Is it even necessary to install the dokku dependencies explicitly as we do here? Wouldn't it be enough to just install dokku, which should then fetch all the necessary dependencies?

[josegonzalez]

@ltalirz should there be a way to use just the libraries from this role? I feel like including them is a mistake, as it makes it so using the libraries always requires running through the install of dokku...

[ltalirz]

@ltalirz should there be a way to use just the libraries from this role? I feel like including them is a mistake, as it makes it so using the libraries always requires running through the install of dokku...

Just to clarify: you're talking about the modules in the libraries folder; not dependencies of the dokku package (the topic of this PR), right?

It is actually possible to use the modules without running the entire role, but it's a bit of a hack (we do this at the verify stage of the tests where it would make no sense to run the role once more:

ansible-dokku/molecule/default/verify.yml

Lines 6 to 9 in cfd3d02

	- name: Run role without running any tasks
	include_role:
	name: dokku_bot.ansible_dokku
	tasks_from: init.yml

).

I haven't kept up much with the latest developments in ansible, but it's possible that using collections would provide a more flexible distribution method. See also the migration guide.

[josegonzalez]

Yeah thats right. I was basically looking for something that could support this new plugin, which currently just deletes the tasks folder.

[ltalirz]

To play around with it, you can use the hack mentioned above.

I guess the "right" way of doing it would be to migrate the role to a dokku collection, which, once installed, would then make the modules available under dokku.dokku_builder I assume. I'll open an issue for it (but I currently don't have the time to do it).

[ltalirz]

Hm... since we switched to empty default values for dokku_version, etc. we haven't had a single complaint. Perhaps it would be fine to just keep the variables and "un-deprecate" them...

[josegonzalez]

Up to you :)