fix(windows): avoid subprocess git calls that hang in pip .exe wrappers

[hamb3r]

Problem

On Windows, pip-installed console_scripts (.exe wrappers) inherit a reduced PATH that often does not include git. Every call to subprocess.run(["git", ...]) either raises FileNotFoundError or hangs until the 10-second timeout.

Since _ensure_index() and _maybe_incremental_update() make multiple git subprocess calls (rev-parse, diff, ls-files), a single tool invocation takes 20+ seconds before returning a result.

Reproduction

1. pip install "mcp-codebase-index[mcp]" on Windows 10/11
2. Configure as MCP server in Claude Code
3. Call any tool → hangs for 20+ seconds on first call

Root cause

is_git_repo() calls git rev-parse --is-inside-work-tree and get_head_commit() calls git rev-parse HEAD via subprocess.run. Inside the .exe wrapper process, git is not on PATH, so these calls hang until timeout.

Solution

Two source files changed, zero new dependencies.

git_tracker.py

Function	Before	After
_resolve_git_dir()	(new)	Unified git-dir resolver: walks up parents, supports .git dir (regular repos) and .git file with gitdir: pointer (worktrees/submodules)
is_git_repo()	subprocess.run(["git", "rev-parse", ...])	Delegates to _resolve_git_dir() — pure filesystem, no subprocess
get_head_commit()	subprocess.run(["git", "rev-parse", "HEAD"])	Uses _resolve_git_dir(), then reads .git/HEAD directly. Supports symbolic refs, detached HEAD, packed-refs, SHA-1 (40 hex) and SHA-256 (64 hex)
_find_git()	(new)	Resolves git binary path once at import time via shutil.which() + Windows fallback paths
get_changed_files()	["git", "diff", ...]	[_GIT_CMD, "diff", ...] using resolved path; new skip_committed kwarg to skip since_ref..HEAD diff while still checking working tree

server.py

Function	Change
_maybe_incremental_update()	Uses skip_committed=True when HEAD hasn't moved instead of early return — working tree changes (unstaged, staged, untracked) are always detected

test_git_tracker.py

Tests fully rewritten for the new filesystem-based implementations:

Test class	Tests	Coverage
TestResolveGitDir	7	.git dir, parent walk, .git file with absolute/relative gitdir:, non-git, invalid .git file, missing target dir
TestIsGitRepo	5	Regular repo, nested path, worktree .git file, non-git, empty path
TestGetHeadCommit	8	Symbolic ref, detached HEAD (SHA-1), detached HEAD (SHA-256), packed-refs, worktree .git file, subdirectory root, no .git dir, missing ref, invalid hash
TestCommitHashRe	5	SHA-1, SHA-256, short hash, non-hex, wrong length
TestFindGit	3	shutil.which success, fallback, bare "git"
TestGetChangedFiles	10	None ref, M/A/D parsing, rename, overlap resolution, untracked, skip_committed skips committed diff, skip_committed still checks working tree, FileNotFoundError
TestGitChangeSet	4	Empty, modified, added, deleted
Total	43

$ python -m pytest tests/test_git_tracker.py -v
======================== 43 passed in 0.10s ========================

Cross-platform safety

• Linux/macOS/Docker: shutil.which("git") resolves immediately; Windows-specific fallback paths are skipped (files don't exist). _resolve_git_dir() filesystem walk is the same logic on all platforms. No behavior change.
• Windows: filesystem-based is_git_repo() and get_head_commit() eliminate the subprocess dependency on hot path. _find_git() resolves git for diff operations.
• Worktrees/Submodules: _resolve_git_dir() follows .git files with gitdir: pointers (both absolute and relative paths).

Result

Metric	Before	After
First tool call (with cache)	~21s	0.2s
First tool call (cold, no cache)	~21s	~1s (indexing only)

Tested on Windows 10 Pro, Python 3.14, pip editable install, Claude Code MCP integration.

[hamb3r]

cc @MikeRecognex