Fix: gke-deploy init container image updates and PDB maxUnavailable readiness

[64johnlee]

Summary

Two related fixes to Kubernetes resource handling in gke-deploy, covering issues that block production deployments.

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Fix 1: Init Container Images Not Updated (Fixes #573)

Problem

UpdateMatchingContainerImage iterated only spec.containers, ignoring spec.initContainers entirely. Init containers have separate image fields and are commonly used for pre-start setup tasks (DB migrations, config fetching, secret injection) whose images need to be updated alongside regular containers.

Root Cause

// Before: only one field path per kind
nestedFields = []string{"spec", "template", "spec", "containers"}  // initContainers never visited

Fix

Restructure the loop to iterate both field paths for each workload kind:

// After: both containers and initContainers processed
for _, nestedFields := range [][]string{containersFields, initContainersFields} { ... }

Covers all affected kinds: Deployment, DaemonSet, Job, ReplicaSet, ReplicationController, StatefulSet, CronJob, Pod

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Fix 2: PodDisruptionBudget Ignores spec.maxUnavailable (Fixes #725)

Problem

podDisruptionBudgetIsReady assumed status.desiredHealthy > 0, which is only true for PDBs using spec.minAvailable. Since Kubernetes 1.17, PDBs can use spec.maxUnavailable instead, which results in desiredHealthy == 0 — causing the readiness check to always return false and block deployments indefinitely.

Root Cause

// Before: ignored the ok bool, assumed desiredHealthy is always meaningful
if !ok || currentHealthy < desiredHealthy {  // false when desiredHealthy == 0
    return false, nil
}

Fix

Detect the minAvailable vs maxUnavailable path:

• desiredHealthy > 0 → minAvailable mode → check currentHealthy >= desiredHealthy
• desiredHealthy == 0 → maxUnavailable mode → confirm readiness by presence of status.disruptionsAllowed, which the API server populates once the PDB is accepted and reconciled

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Files Changed

• gke-deploy/core/resource/resource.go — init container field paths added to UpdateMatchingContainerImage
• gke-deploy/core/resource/ready.go — PDB readiness logic split into minAvailable / maxUnavailable paths

Backward Compatibility

Both fixes are purely additive:

• Init container update: only affects workloads that have initContainers; others unchanged
• PDB fix: minAvailable path logic unchanged; maxUnavailable path is new

🤖 Generated with Claude Code

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