fix(project): case-sensitive isGitRepo + injectable GitChecker

[neversettle17-101]

Summary

Resolves the two isGitRepo findings deferred from #95 / PR #96 (an implementation existed there and was reverted in e3d2533; this restores it).

1. Case-sensitivity bug on Linux

The old isGitRepo used strings.EqualFold(top, path), which wrongly treats /home/u/MyRepo and /home/u/myrepo as the same path on case-sensitive filesystems. Replaced with samePath, which is case-insensitive only on darwin/windows (gated by runtime.GOOS) and uses == everywhere else.

2. Untestable git check

The git check shelled out to exec.Command("git", ...) directly, so project.Service couldn't be tested without a real git binary and working tree. The check now sits behind a GitChecker interface injected into Service:

• execGitChecker — production impl, shells out to git.
• NewWithGitChecker(store, git) — lets tests substitute a fake.

Tests

• TestAdd_UsesInjectedGitChecker / TestAdd_RejectsNonRepoViaGitChecker — exercise Add through a fake GitChecker, no git binary.
• TestSamePath_CaseSensitivity — guards the platform contract for samePath.

Acceptance criteria

• isGitRepo correct on case-sensitive filesystems
• Project service testable without a real git binary

Closes #97

🤖 Generated with Claude Code

[greptile-apps]

Greptile Summary

Introduces a GitChecker interface injected into Service, moving the git binary shell-out to a swappable seam, and fixes a case-sensitivity bug in the old isGitRepo by replacing unconditional strings.EqualFold with samePath, which uses case-insensitive comparison only on darwin/windows and strict == on Linux.

• git.go defines GitChecker, execGitChecker (production), and samePath with the platform-gated logic; the free-function isGitRepo wrapper continues to serve workspace_registration.go, which is explicitly out of scope for this injection.
• service.go gains a git GitChecker field, a NewWithGitChecker constructor, and swaps isGitRepo(path) for m.git.IsRepo(path) in Add.
• git_test.go / export_test.go add unit tests for the injected checker and the samePath platform contract, both exercisable without a real git binary.

Confidence Score: 5/5

Safe to merge; the refactor is well-scoped, backward-compatible, and all changed paths are covered by tests.

The case-sensitivity fix replaces a clear incorrect behaviour with a correct platform-gated implementation. The GitChecker injection follows a clean constructor-injection pattern; New delegates to NewWithGitChecker so no call sites break. The free-function isGitRepo wrapper is still reachable from workspace_registration.go so there is no dead code. Tests exercise both the happy path and the rejection path through the fake seam.

No files require special attention.

Important Files Changed

Filename	Overview
backend/internal/service/project/git.go	New file; correctly extracts GitChecker interface, execGitChecker production impl, and platform-aware samePath. isGitRepo free function confirmed used by workspace_registration.go.
backend/internal/service/project/service.go	Adds git GitChecker field, NewWithGitChecker constructor, and replaces direct isGitRepo call with m.git.IsRepo; backward-compatible via New delegating to NewWithGitChecker.
backend/internal/service/project/git_test.go	Adds three focused tests: injectable checker acceptance, rejection path, and samePath platform contract — none require a real git binary.
backend/internal/service/project/export_test.go	Cleanly exposes samePath via SamePathForTest without widening the package's public surface; standard Go export_test pattern.

_{Reviews (3): Last reviewed commit: "test(project): drop real-git assertion f..." | Re-trigger Greptile}