[deckhouse-cli] Run kubectl plugins from d8 k

[yalosev]

Description

d8 k now runs kubectl plugins: d8 k argo rollouts get rollout demo runs kubectl-argo-rollouts get rollout demo, the same as kubectl argo rollouts get rollout demo. This also works through the kubectl alias that Deckhouse adds on nodes.

Why do we need it, and what problem does it solve?

Starting with Deckhouse 1.76, nodes no longer get a separate kubectl binary. /root/.bashrc aliases kubectl to /opt/deckhouse/bin/d8 k. With that alias in place, kubectl plugins on the nodes stopped working. A client reported this for the argo-rollouts plugin (/usr/local/bin/kubectl-argo-rollouts).

The cause: d8 k passed the whole d8 command line to kubectl's plugin lookup. The word k ended up in the plugin name, so d8 k argo rollouts get searched PATH for kubectl-k-argo-rollouts.

Technical details

NewKubectlCommand passes kubectlPluginArgs(os.Args) to the plugin handler:

d8 command line	passed to the lookup	plugin found
d8 k argo rollouts get	d8 argo rollouts get	kubectl-argo-rollouts
d8 kubectl argo rollouts version	d8 argo rollouts version	kubectl-argo-rollouts
d8 k create foo bar	d8 create foo bar	kubectl-create-foo
any other d8 <cmd> ...	d8	lookup disabled

The last row matters. d8 builds the kubectl command tree on every run, so before this change d8 <name> ran kubectl-<name> from PATH for this tree too.

The same lookup is also present in the delivery-kit dependency. github.com/deckhouse/delivery-kit/v2 cmd/werf/kubectl/kubectl.go builds the d8 dk kubectl tree with Arguments: os.Args, so d8 hello still runs kubectl-hello when that file is in PATH. It is fixed separately in deckhouse/delivery-kit#408 (main, v3) and deckhouse/delivery-kit#409 (2, the v2 line d8 depends on); d8 picks the fix up when it bumps delivery-kit.

Clients who added a kubectl-k-<name> symlink as a workaround need no changes: the original plugin it points to is in PATH and is now found by its own name.

What is the expected result?

With kubectl-argo-rollouts and kubectl-create-foo test scripts in PATH:

Command	Before (d8 v0.31.0)	After
d8 k argo rollouts get rollout demo -n app	kubectl help	kubectl-argo-rollouts get rollout demo -n app
d8 kubectl argo rollouts version	kubectl help	kubectl-argo-rollouts version
d8 k create foo bar	error: Unexpected args: [foo bar]	kubectl-create-foo bar
d8 k version --client	client version	client version

Tests:

• go test ./cmd/commands/ passes;
• TestKubectlPluginLookup fails on the old code in all three cases;
• golangci-lint v2.11.4 on ./cmd/commands/ reports 0 issues.