Support use with Docker

[eemcmullan]

Right now, kantra defaults to podman to run commands in containers. An env var PODMAN_BIN can be used to override it with docker. We want to allow kantra to detect docker use, if available, without the user having to define this variable.

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[ascheman]

Wouldn't it be sufficient to replace the one and only (currently) call to the podman (docker) binary by a suitable use of a respective library, e.g., https://pkg.go.dev/github.com/docker/docker/client?

Then only the installation guide (README.md) would be left with a hard coded use of podman to set up Kantra.

[shawn-hurley]

IIUC, and please correct me if I am incorrect; the docker engine client uses the API to call into a docker to take action.

While this is also supported in Podman, I can't see this as a shared, agreed-on spec in OCI. While I doubt this would change, it is just something I am a little worried about. Specifically, I am looking at this part of the [https://github.com/opencontainers/runtime-spec/blob/main/glossary.md#runtime-caller]

Runtime callers often execute a runtime via runc-compatible command line interface; however, its interaction interface is currently out of the scope of the Open Container Initiative Runtime Specification.

It sounds like there are no defined specs for external callers, but I feel like I would be more comfortable using the CLI interface because of the line around runc.

Like I said I could be incorrect, and if there is some other place to look please point me to it, I honestly have no idea, just thoughts on what I am reading.

There is also the concern about having a dependency on Moby, as, in the past, this has caused me lots of pain. It may not be a real concern anymore just some past experience that I want to add to the conversation.

[eemcmullan]

Resolved in #165

[ascheman]

If I look into the code of #165, I wonder how I could enforce using docker via ${PODMAN_BIN} if there is a podman on the path?

[shawn-hurley]

https://github.com/konveyor/kantra/pull/165/files#diff-33b6837c599c9f67320ec38678d366528089e4a5db0f786203c3af5c9898bd66R45-R47

If PODMAN_BIN is set, it will use that AFAICT

[ascheman]

Of course, your right as the Load() function only makes sure the path is known/set to the Config struct ...