Git Credential Manager (GCM) installed by Git for Windows tries to open
an interactive credential prompt or wincredman store — both fail in a
WinRM session (no TTY, no interactive desktop).
Fix:
- Set GIT_TERMINAL_PROMPT=0 to suppress all interactive git prompts
- Prepend '-c credential.helper=' (empty string) to reset the helper chain
before injecting our store-based helper (clearing GCM from the chain)
- Custom credential helper (store --file <tmp>) then appended only when PAT present
Without PAT (public repo): GCM still cleared, no prompt attempted, clean fail
if auth is actually required.
With PAT: store-based helper used exclusively, GCM never invoked.