feat: allow helmfile to continue on failed releases (#2616)

* feat: allow helmfile to continue on failed releases

Co-authored-by: Peter Honeder <peter.honeder@unwired.at>
Signed-off-by: Niklas Ott <niklas.ott@unwired.at>

* fix: skip failed-prep releases, complete flag wiring, add tests and docs (#64)

Review follow-ups for --allow-failed-releases (#2616):

- Track per-release chart preparation failures in PrepareCharts (returned
  as a map keyed by release) and remove those releases from the state in
  Run.WithPreparedCharts when --allow-failed-releases is set, so a failed
  release is never executed against its original, un-prepared chart
  reference (which could either fail again with a duplicate error or, for
  charts requiring chartify, bypass patches/dependency modifications and
  produce an unintended result). All failures are still reported at the
  end via the aggregated MultiError.
- Complete the release identity on error results from
  prepareChartForRelease so failures are attributed to the correct
  release.
- With --allow-failed-releases, continue building dependencies of the
  remaining charts when 'helm dep build' fails for one release, and skip
  the affected releases during execution.
- Wire --allow-failed-releases into 'helmfile unittest' and 'helmfile
  status'; remove the dead flag wiring for write-values and list (both
  never prepare charts, see commandsSkipChartPrep).
- Simplify control flow (guard clauses, errors.As, drop dead code and
  redundant else branches).
- Add end-to-end coverage in pkg/app/issue_2616_test.go and extend the
  state-level tests; document the flag in docs/cli.md and CHANGELOG.md.

Signed-off-by: yxxhero <11087727+yxxhero@users.noreply.github.com>

---------

Signed-off-by: Niklas Ott <niklas.ott@unwired.at>
Signed-off-by: yxxhero <11087727+yxxhero@users.noreply.github.com>
Co-authored-by: Peter Honeder <peter.honeder@unwired.at>
Co-authored-by: yxxhero <11087727+yxxhero@users.noreply.github.com>

pkg/app/diff_test.go

@@ -25,6 +25,7 @@ type diffConfig struct {
 	skipCRDs                 bool
 	skipDeps                 bool
 	skipRefresh              bool
+	allowFailedReleases      bool
 	includeTests             bool
 	skipNeeds                bool
 	includeNeeds             bool
@@ -87,6 +88,10 @@ func (a diffConfig) SkipRefresh() bool {
 	return a.skipRefresh
 }
 
+func (a diffConfig) AllowFailedReleases() bool {
+	return a.allowFailedReleases
+}
+
 func (a diffConfig) IncludeTests() bool {
 	return a.includeTests
 }