feat: add --repo-retries for helm repo and registry login commands (#2683)

* feat: add --repo-retries for retrying helm repo and registry login commands

Add a configurable retry mechanism for chart repository operations to
handle unstable networks (corporate proxies, slow internal registries).

Closes #1894

- New --repo-retries N flag and HELMFILE_REPO_RETRIES env var (default 0
  = opt-in, backward compatible)
- Retry applies to helm repo add, helm repo update (incl. ACR), and
  helm registry login with exponential backoff (1s, 2s, 4s, ..., capped 30s)
- Single retryRepoOp helper; per-attempt args/buffer are local to avoid
  state leaking across retries
- Tests cover succeed-after-retry, exhausted-retries, disabled-by-default,
  and regression guards for password-buffer and args-accumulation

Signed-off-by: yxxhero <aiopsclub@163.com>

* fix: address PR review (overflow guard, cancellable sleep, flag-override, docs)

Address Copilot review feedback on #2683:

- Cap backoff shift exponent at 5 to prevent time.Duration overflow on
  large --repo-retries values
- Make retry sleep context-aware (sleepCtx) so Ctrl+C aborts the retry
  loop promptly via the ShellRunner context
- Log a concise exit status instead of the verbose ExitError dump, and
  clarify the retry-counter wording ('retry N/M')
- Use -1 sentinel as the CLI default so --repo-retries=0 can explicitly
  disable retries even when HELMFILE_REPO_RETRIES is set
- Align help text and docs: retry applies 'on failure' (not just
  transient errors), document the 0-disables behavior
- Add tests for overflow guard, cancellable sleep, and flag-zero-disables

Signed-off-by: yxxhero <aiopsclub@163.com>

* fix: abort retries on canceled context, hide sentinel default, align comment

Address follow-up Copilot review on #2683:

- Fix tight-loop bug: sleepCtx now returns whether it completed vs was
  interrupted by context cancellation, and retryRepoOp aborts the retry
  loop on interruption so Ctrl+C no longer spins into rapid helm calls
- Hide the -1 sentinel from --help by overriding the displayed default
  to 0 (pflag DefValue), matching the documented default while keeping
  the flag-override semantics
- Correct HelmExecOptions.RepoRetry comment: 'on failure' not 'transient
  network errors', matching the actual retry behavior
- Add Test_Retry_AbortsOnCanceledContext covering the no-tight-loop path

Signed-off-by: yxxhero <aiopsclub@163.com>

* fix: copy args per retry in RegistryLogin, make cancel test deterministic

Address follow-up Copilot review on #2683:

- RegistryLogin: pass a per-attempt copy of args to execStdIn so its
  internal append (for helm.extra) can't alias the shared slice across
  retries
- Test_Retry_AbortsOnCanceledContext: cancel the context deterministically
  inside the op closure after the first attempt, replacing the flaky
  time.Sleep(20ms) goroutine

Signed-off-by: yxxhero <aiopsclub@163.com>

* fix: return error on unknown managed repo type instead of silent skip

Address Copilot review on #2683: AddRepo logged an error for an unknown
managed type but returned nil, silently succeeding while skipping the
repo add. Now returns an error so misconfigurations fail loudly.

Signed-off-by: yxxhero <aiopsclub@163.com>

---------

Signed-off-by: yxxhero <aiopsclub@163.com>

pkg/app/app.go

@@ -37,6 +37,7 @@ type App struct {
 	DisableForceUpdate              bool
 	EnforcePluginVerification       bool
 	HelmOCIPlainHTTP                bool
+	RepoRetry                       int
 	DisableKubeVersionAutoDetection bool
 	SequentialHelmfiles             bool
 
@@ -87,6 +88,7 @@ func New(conf ConfigProvider) *App {
 		DisableForceUpdate:         conf.DisableForceUpdate(),
 		EnforcePluginVerification:  conf.EnforcePluginVerification(),
 		HelmOCIPlainHTTP:           conf.HelmOCIPlainHTTP(),
+		RepoRetry:                  conf.RepoRetry(),
 		SequentialHelmfiles:        conf.SequentialHelmfiles(),
 		Logger:                     conf.Logger(),
 		Kubeconfig:                 conf.Kubeconfig(),
@@ -983,6 +985,7 @@ func (a *App) getHelm(st *state.HelmState) (helmexec.Interface, error) {
 			DisableForceUpdate:        a.DisableForceUpdate,
 			EnforcePluginVerification: a.EnforcePluginVerification,
 			HelmOCIPlainHTTP:          a.HelmOCIPlainHTTP,
+			RepoRetry:                 a.RepoRetry,
 		}, a.Logger, kubeconfig, kubectx, &helmexec.ShellRunner{
 			Logger:                     a.Logger,
 			Ctx:                        a.ctx,

pkg/app/config.go

@@ -15,6 +15,7 @@ type ConfigProvider interface {
 	DisableForceUpdate() bool
 	EnforcePluginVerification() bool
 	HelmOCIPlainHTTP() bool
+	RepoRetry() int
 	SkipDeps() bool
 	SkipRefresh() bool
 	SequentialHelmfiles() bool