argoproj/argo-cd

Sources and tooling

Argo CD supports plain-YAML directories, Helm charts (HTTP and OCI), Kustomize bases/overlays, OCI artifacts, and arbitrary Config Management Plugins. This page traces how each renderer is selected and where its code lives.

Source detection

reposerver/repository/repository.go is where the repo server decides which renderer to invoke. The decision tree (simplified):

graph TD
    Source[ApplicationSource] --> IsOCI{OCI URL?}
    IsOCI -- yes --> OCI[util/oci]
    IsOCI -- no --> IsHelmField{source.helm set\nor chart present?}
    IsHelmField -- yes --> Helm[util/helm]
    IsHelmField -- no --> IsKustomize{kustomization.yaml found\nor source.kustomize set?}
    IsKustomize -- yes --> Kustomize[util/kustomize]
    IsKustomize -- no --> IsPlugin{source.plugin or sidecar match?}
    IsPlugin -- yes --> CMP[util/cmp + cmpserver]
    IsPlugin -- no --> Directory[Directory of YAML/JSON]

Helm

Path	Purpose
`util/helm/helm.go`	Higher-level helpers used by the repo server.
`util/helm/cmd.go`	Wrapper around the `helm` CLI.
`util/helm/client.go`	Helm chart repo and OCI registry client.
`util/helm/creds.go`	Auth: basic, bearer, OCI.
`util/helm/index.go`	Parses `index.yaml` for chart catalogs.

Argo CD supports Helm 3 charts from:

Classic chart repos (https://charts.example.com) with index.yaml.
OCI registries (any oci://... URL).
Direct chart sources inside Git repos (Chart.yaml in the source path).

Values can be inline, taken from values files in the same source, or merged from a different value source (multi-source applications).

Kustomize

Path	Purpose
`util/kustomize/kustomize.go`	Wraps `kustomize build` and post-processes the output.

Argo CD supports Kustomize image overrides, namespace overrides, common labels/annotations, replicas overrides, and inline patches via the source.kustomize block.

Directory of YAML/JSON

The repo server walks the source path and returns every YAML/JSON manifest. Helpful flags:

--include-hidden-directories — include .foo directories.
--allow-out-of-bounds-symlinks — relax the default symlink safety check.
Glob filters via the argocd.argoproj.io/manifest-generate-paths annotation.

A directory source can also evaluate Jsonnet (*.jsonnet).

OCI artifacts

util/oci/client.go implements a client capable of pulling pure OCI artifacts (not Helm charts) and extracting their layers as manifest sources. Combined with util/oci/registry.go, this supports docker.io / GHCR / ECR / GAR / Quay.

Config Management Plugins (CMP)

util/cmp/ and cmpserver/ host the plugin runtime. See CMP server for the protocol. The repo server matches a plugin by:

A source.plugin.name reference, or
The plugin's discover rules (file globs or shell commands) when the user opted into "auto-discovery".

OCI helm registries (legacy compat)

Helm OCI usage is one of the most-tweaked code paths because of subtle protocol differences across registries. util/helm/client.go and util/oci/client.go both contain registry-specific quirks (anonymous tokens for ECR, retry logic for transient 401s).

Multi-source applications

Application.spec.sources (in pkg/apis/application/v1alpha1/types.go) lets a single Application combine multiple sources. Common patterns:

Helm chart from one repo, values files from another.
Helm chart + a directory of supplemental manifests.
Kustomize base from one repo, overlays from another.

The repo server renders each source in turn and the controller composes the result before applying.