feat: Allow custom User-Agent headers for Helm repository requests

[yugannkt]

Allow custom User-Agent headers for Helm repository requests

Adds support for configuring custom HTTP User-Agent headers for Helm repository requests. This enables users to identify and track requests from ArgoCD, meet server requirements, or debug connectivity issues.

Closes #25459

Motivation

Some Helm repositories and OCI registries require or recommend specific User-Agent headers for:

• Request tracking and analytics
• Rate limiting and access control policies
• Debugging and troubleshooting connectivity issues
• Compliance with internal organizational standards

Currently, ArgoCD uses default HTTP client User-Agent values that may not meet these requirements.

Changes

Core Implementation

• Added UserAgent field to Repository CRD (pkg/apis/application/v1alpha1/repository_types.go)
• Implemented User-Agent header support in Helm client for both traditional and OCI registries (util/helm/client.go, util/helm/creds.go)
• Added priority handling: code-level > per-repository > default

CLI Support

• Added --user-agent flag to argocd repo add command
• Updated CLI command structure in cmd/util/repo.go and cmd/argocd/commands/repo.go

Documentation

• Updated operator manual with declarative configuration examples (docs/operator-manual/declarative-setup.md)
• Added user guide section with CLI and YAML examples (docs/user-guide/private-repositories.md)
• Auto-generated CLI documentation updated

Testing

• Added comprehensive test suite in util/helm/client_test.go:
  • TestUserAgentIsSet - Verifies default and custom User-Agent
  • TestUserAgentRequiredByServer - Tests server requirements
  • TestUserAgentPriority - Validates precedence rules
• All new tests passing

Example Usage

CLI

argocd repo add https://charts.example.com --type=helm --user-agent="my-custom-agent/1.0"

Declarative

apiVersion: v1
kind: Secret
metadata:
  name: helm-repo
  namespace: argocd
  labels:
    argocd.argoproj.io/secret-type: repository
stringData:
  name: my-helm-repo
  url: https://charts.example.com
  type: helm
  userAgent: my-custom-agent/1.0

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this does not need to be in the release notes.
• The title of the PR states what changed and the related issues number (used for the release note).
• The title of the PR conforms to the Title of the PR
• I've included "Closes [ISSUE #]" or "Fixes [ISSUE #]" in the description to automatically close the associated issue.
• I've updated both the CLI and UI to expose my feature, or I plan to submit a second PR with them.
• Does this PR require documentation updates?
• I've updated documentation as required by this PR.
• I have signed off all my commits as required by DCO
• I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged.
• My new feature complies with the feature status guidelines.
• I have added a brief description of why this PR is necessary and/or what this PR solves.
• Optional. My organization is added to USERS.md.
• Optional. For bug fixes, I've indicated what older releases this fix should be cherry-picked into (this may or may not happen depending on risk/complexity).
• My build is green (troubleshooting builds).

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[codecov]

Codecov Report

❌ Patch coverage is 90.47619% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 62.52%. Comparing base (3bf3d8a) to head (fa6150d).

Files with missing lines	Patch %	Lines
reposerver/repository/repository.go	0.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #25473      +/-   ##
==========================================
+ Coverage   62.49%   62.52%   +0.02%     
==========================================
  Files         351      351              
  Lines       49602    49620      +18     
==========================================
+ Hits        31001    31026      +25     
+ Misses      15631    15621      -10     
- Partials     2970     2973       +3     

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[blakepettersson]

I think this should be set as an environment variable on the repo-server rather than being set on the repository.

[yugannkt]

Thank you for the feedback! I'd like to understand your reasoning better before refactoring.

Questions:

1. Would you prefer a single global User-Agent for all Helm repos, or should there be a way to override per-repository?
2. Are there specific concerns with the current per-repository approach?
3. Would a hybrid approach (env var as default + per-repo override) make sense?

My concern: Other repo-specific configs (credentials, proxy, TLS) are set per-repository. Would an env-var-only approach be inconsistent? Or is User-Agent different enough that it should be global?

Thanks!

[blakepettersson]

Would you prefer a single global User-Agent for all Helm repos, or should there be a way to override per-repository?

IMO this should be a global option. Up until now there has been no need for setting a header for a Helm repository, and I don't anticipate there will be much of a need to configure this on a per repository basis either.

Are there specific concerns with the current per-repository approach?

We already have too many options on the Repository object as-is.

Would a hybrid approach (env var as default + per-repo override) make sense?

No

[yugannkt]

Hy @blakepettersson

Refactored per feedback - Changed from per-repository User-Agent configuration to a global environment variable approach, Please review it

Thank you :)

[blakepettersson]

See comment

[yugannkt]

Hy @blakepettersson

All requested changes have been addressed:

The Helm User-Agent is now set globally via the repo-server using the ARGOCD_HELM_USER_AGENT environment variable.
Please review it :)