Add GitHub Enterprise Server (GHES) support (self-hosted GitHub)

[phmatray]

Summary

Please add support for GitHub Enterprise Server (GHES) in Auto-Claude so the tool can be used with self-hosted GitHub instances (e.g., https://github.company.tld) in addition to github.com.

Problem / Motivation

Many organizations run GHES for security/compliance and cannot use GitHub.com. Today, Auto-Claude appears to assume GitHub.com defaults (API base URL, auth endpoints, clone URLs, etc.), which prevents adoption in enterprise environments.

Proposed Solution

Introduce a configurable GitHub host and derive all GitHub-related URLs from it:

• GITHUB_HOST (e.g., github.company.tld)
• GITHUB_BASE_URL (e.g., https://github.company.tld)
• GITHUB_API_URL (e.g., https://github.company.tld/api/v3)

Implementation notes (suggested)

1. Centralize URL building

   • Use a single helper to build:
     • REST API base URL (/api/v3)
     • Web URLs (repo links, PR links, etc.)
     • Git clone URLs (HTTPS/SSH)

2. Token authentication

   • Support standard GHES PATs with Authorization: token <PAT> (or Bearer if you already use it).
   • Ensure scopes/documentation match what Auto-Claude needs (e.g., repo read/write, PR creation, checks/statuses).

3. Make it easy to configure

   • Environment variables or config file support (prefer env vars for CI).
   • Default remains GitHub.com when no host is provided.

4. Documentation

   • Add a short section: “Using GitHub Enterprise Server”
   • Include examples for:
     • github.company.tld
     • https://github.company.tld/api/v3

Acceptance Criteria

• Works against a GHES instance when GITHUB_HOST (or equivalent) is set:
  • Auth succeeds
  • Repos can be accessed
  • PRs/comments/status updates (whatever Auto-Claude does today) function correctly
• No regressions for GitHub.com users (defaults unchanged)
• Documentation includes configuration examples for GHES
• (Nice-to-have) Add a CI test or a small integration harness that can run against a mocked GitHub API base URL

Additional Context

GHES differs from GitHub.com primarily via the REST API base path (/api/v3) and hostnames. This feature would unlock enterprise usage without changing core functionality.

[hanqyu]

I'm waiting for this!