Test and document environment inside container step with current shortcomings

[Vlatombe]

Testing done

Submitter checklist

Preview Give feedback

1. Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
2. Ensure that the pull request title represents the desired changelog entry
3. Please describe what you did
4. Link to relevant issues in GitHub or Jira
5. Link to relevant pull requests, esp. upstream and downstream changes
6. Ensure you have provided tests - that demonstrates feature works or fixes the issue

[jglick]

I suspect the problem is that some code such as

kubernetes-plugin/src/main/java/org/csanchez/jenkins/plugins/kubernetes/pipeline/ContainerExecDecorator.java

Lines 338 to 348 in 6ab2953

	EnvVars environment = computer.getEnvironment();
	if (environment != null) {
	Set<String> overriddenKeys = new HashSet<>();
	for (String keyValue : envVars) {
	String[] split = keyValue.split("=", 2);
	if (!split[1].equals(environment.get(split[0]))) {
	// Only keep environment variables that differ from Computer's environment
	resultEnvVar.add(keyValue);
	overriddenKeys.add(split[0]);
	}
	}

does not belong in this class at all, and should instead be in

kubernetes-plugin/src/main/java/org/csanchez/jenkins/plugins/kubernetes/pipeline/ContainerStepExecution.java

Lines 51 to 53 in 6ab2953

	EnvironmentExpander env = EnvironmentExpander.merge(
	getContext().get(EnvironmentExpander.class),
	EnvironmentExpander.constant(Collections.singletonMap("POD_CONTAINER", containerName)));

#1486 (comment) might make this more apparent.