Azure Repos: Automatically fall back to OAuth tokens when PAT creation is blocked by org policy

Problem:-

When an Azure DevOps organization has a policy that disables PAT creation (disablePatCreationPolicy), GCM fails with an error during
GeneratePersonalAccessTokenAsync() with no recovery path. The user must manually discover and set:

git config --global credential.azreposCredentialType oauth

This is a poor experience because:-

• The error message doesn't suggest the workaround
• The user has already successfully authenticated via AAD/Entra ID (the OAuth token was obtained), but the subsequent PAT creation step fails
• The fix is simple - use the OAuth token directly - but users don't know this

Current Behaviour:-

1. GCM detects Azure DevOps host
2. UsePersonalAccessTokens() returns true (default on non-DevBox platforms)
3. GeneratePersonalAccessTokenAsync() successfully obtains an AAD access token
4. CreatePersonalAccessTokenAsync() calls _apis/token/sessiontokens → fails due to org policy
5. Trace2Exception propagates to the user — no fallback, no helpful guidance

Expected Behavior:-

When PAT creation fails due to an organization policy block, GCM should:

1. Detect the specific policy-block failure (via HTTP status code and/or error message)
2. Log a warning: "PAT creation blocked by organization policy, falling back to OAuth tokens"
3. Fall back to returning the OAuth/AAD access token directly (same path as credential.azreposCredentialType=oauth)

Environment

• OS: macOS (but affects all non-DevBox platforms)
• GCM version: latest
• Azure DevOps org: Has disablePatCreationPolicy enabled
• Auth method: az login via Entra ID

Proposed Fix:-

In AzureReposHostProvider.cs → GetCredentialAsync(), wrap the GeneratePersonalAccessTokenAsync() call in a try/catch that detects the policy-block error and falls
back to GetAzureAccessTokenAsync().

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I'm happy to submit a PR for this. Before I do, could you confirm:

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1. What HTTP status code / error message does _apis/token/sessiontokens return when blocked by org policy? (I can capture this with GCM_TRACE=1 if needed)
2. Is this the right approach, or would you prefer a different fallback strategy?

Start in AzureReposHostProvider.cs and trace GetCredentialAsync() through GeneratePersonalAccessTokenAsync(), CreatePersonalAccessTokenAsync(), and GetAzureAccessTokenAsync(). Use GCM_TRACE=1 to identify the policy-block response from _apis/token/sessiontokens. Done means policy-block failures are recognized, a warning explains the fallback, and OAuth credentials are returned without affecting other PAT errors.