Add Azure Workload Identity Federation auth for Azure DevOps

[namnt2307]

What

Adds a secretless authentication mode for Azure DevOps Services repos using Azure Workload Identity Federation. When --azure-workload-identity is set, git-sync exchanges the pod's projected ServiceAccount token with Microsoft Entra ID for a short-lived access token and uses it as the git credential — no PAT, SSH key, or long-lived secret is stored. Mirrors the existing GitHub App auth mode.

Why

Implements the request in #955: environments whose policies forbid PATs currently can't use git-sync with Azure DevOps even when the workload identity already has repo access.

Config

New flags (each with GITSYNC_* and AZURE_* env fallbacks):

• --azure-workload-identity — opt in
• --azure-client-id / --azure-tenant-id / --azure-federated-token-file / --azure-authority-host — default to the AZURE_* vars injected by the azure-workload-identity webhook; overridable as flags
• --azure-scope — defaults to the Azure DevOps resource ID

Docs in docs/azure-workload-identity.md; flags documented in README.md.

Testing

• Unit tests exercise the Entra token exchange and endpoint construction against an httptest fake — no real Azure required, per the maintainer note in Feature Request: Support Azure DevOps Git Repos via Managed Identity (WIF) Authentication #955.
• Manually verified end-to-end against real Entra ID + Azure DevOps: a pod's federated token successfully clones a private ADO repo.

Ref #955

[kubernetes-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: namnt2307
Once this PR has been reviewed and has the lgtm label, please assign stp-ip for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[kubernetes-prow]

Welcome @namnt2307!

It looks like this is your first PR to kubernetes/git-sync 🎉. Please refer to our pull request process documentation to help your PR have a smooth ride to approval.

You will be prompted by a bot to use commands during the review process. Do not be afraid to follow the prompts! It is okay to experiment. Here is the bot commands documentation.

You can also check if kubernetes/git-sync has its own contribution guidelines.

You may want to refer to our testing guide if you run into trouble with your tests not passing.

If you are having difficulty getting your pull request seen, please follow the recommended escalation practices. Also, for tips and tricks in the contribution process you may want to read the Kubernetes contributor cheat sheet. We want to make sure your contribution gets all the attention it needs!

Thank you, and welcome to Kubernetes. 😃