N/A

Description

Several git.Client tests emulate Git by re-executing the test binary with hand-authored output. This makes the tests describe the mock protocol rather than repository behavior, slows race runs, and breaks coverage instrumentation when helper subprocesses discard Go's coverage environment.

This adds a small hermetic temporary-repository harness and converts a pilot cluster covering current branches, config, working-tree changes, remote URLs, ignore rules, and remote resolution. Narrow fakes remain for non-portable failures and exact -- argument-safety contracts. Helper subprocesses now inherit the parent environment so package coverage works.

How did you test this change?

Not tested manually because this refactors test implementation only and does not change production behavior.

Key points

The temporary repositories are sequential because Git configuration isolation currently uses t.Setenv. Synthetic tests remain only where real Git cannot portably produce a precise error or where exact command construction is the safety contract.

Notes for reviewers

Start with newTestRepo and its run helper, then review the converted scenarios. This is stack layer 1; stack metadata will be registered separately after the remaining layers exist.

Authorship and follow-up

Who wrote this:

• A human wrote it.
• An agent wrote it under close human direction.
• An agent wrote it independently, and no human has guided the implementation beyond the initial prompt.

Who answers review comments:

• @williammartin will read and reply directly. Name the account.
• An agent will draft replies and @username will read them before they are posted.
• Nobody has explicitly committed to replying.