Fix | App-of-apps children honor --redirect-target-revisions (#446)

[tobrien-nydig]

Summary

Fixes #446.

With --traverse-app-of-apps + --render-method=repo-server-api, child Applications discovered during traversal were always redirected to the base/target branch, regardless of --redirect-target-revisions. The flag was only honored for top-level (seed) Applications.

Root cause

--redirect-target-revisions is honored in RedirectSources/RedirectGenerators:

shouldRedirect := len(redirectRevisions) == 0 || slices.Contains(redirectRevisions, targetRev)

But during traversal, children were patched with redirectRevisions = nil in renderAppWithChildDiscovery (pkg/reposerverextract/appofapps.go). nil → len(redirectRevisions) == 0 → shouldRedirect = true for every child source, so the filter never applied to traversed children.

When a child source is pinned to a ref that isn't in the list (e.g. a feature branch holding Helm value files absent from the base branch), it was redirected to the PR/base branch and failed to render — failing the whole run.

Fix

Thread the configured redirectRevisions from RenderApplicationsFromBothBranchesWithAppOfApps through renderAppWithChildDiscovery to every child PatchApplication call (the Application case, the ApplicationSet pre-expansion patch, and each ApplicationSet-generated Application). Children now go through the same RedirectSources/RedirectGenerators filter as seed Applications.

The single-Application child patching is extracted into a small buildChildApplication helper, which is covered by unit tests.

Behavior change

• Child source pinned to a revision not in --redirect-target-revisions → left untouched, fetched from its real ref (previously: always redirected).
• Child source pinned to a revision in the list → redirected to the target branch (unchanged).
• No --redirect-target-revisions configured → every matching source still redirected (unchanged default).

Testing

• New unit tests in pkg/reposerverextract/appofapps_test.go:
  • TestBuildChildApplication_LeavesUnlistedRevisionUntouched
  • TestBuildChildApplication_RedirectsListedRevision
  • TestBuildChildApplication_EmptyListRedirectsAll
• go build ./..., go vet, and go test ./pkg/reposerverextract/ ./pkg/argoapplication/ ./cmd/ all pass.

Also documents the behavior in docs/app-of-apps.md.

[dag-andersen]

Looks good 👏🏻