fix(git): auto-detect repo root from --repository

src/git/README.md

@@ -119,6 +119,12 @@ python -m mcp_server_git
 
 ## Configuration
 
+`--repository` accepts any path inside a Git working tree. On startup the server walks up to the enclosing `.git/`, the same way `git rev-parse --show-toplevel` does. So `--repository .` works when a shared config is run from any subdirectory of the repo.
+
+Note that this also means `--repository /repo/subdir` resolves to `/repo` and allows tool calls anywhere under it. If the resolved path differs from the input, startup logs show the rewrite. If you want to restrict operations to a subtree, this flag alone won't do it; use a separate repo or an external sandbox.
+
+Per-tool `repo_path` arguments are not resolved this way and must point at the repo root.
+
 ### Usage with Claude Desktop
 
 Add this to your `claude_desktop_config.json`:

src/git/src/mcp_server_git/server.py

@@ -234,6 +234,14 @@ def git_show(repo: git.Repo, revision: str) -> str:
             output.append(d.diff)
     return "".join(output)
 
+def resolve_repo_root(path: Path) -> Path:
+    """Return the enclosing repo root for ``path``, like ``git rev-parse --show-toplevel``."""
+    repo = git.Repo(path, search_parent_directories=True)
+    if repo.working_dir:
+        return Path(repo.working_dir)
+    return Path(path).resolve()
+
+
 def validate_repo_path(repo_path: Path, allowed_repository: Path | None) -> None:
     """Validate that repo_path is within the allowed repository path."""
     if allowed_repository is None:
@@ -295,11 +303,14 @@ async def serve(repository: Path | None) -> None:
 
     if repository is not None:
         try:
-            git.Repo(repository)
-            logger.info(f"Using repository at {repository}")
+            resolved = resolve_repo_root(repository)
         except git.InvalidGitRepositoryError:
-            logger.error(f"{repository} is not a valid Git repository")
+            logger.error(f"{repository} is not inside a Git repository")
             return
+        if resolved != repository:
+            logger.info(f"Resolved --repository {repository} to repo root {resolved}")
+        repository = resolved
+        logger.info(f"Using repository at {repository}")
 
     server = Server("mcp-git")
 

src/git/tests/test_server.py

@@ -1,3 +1,5 @@
+import asyncio
+import logging
 import pytest
 from pathlib import Path
 import git
@@ -15,6 +17,8 @@
     git_log,
     git_create_branch,
     git_show,
+    resolve_repo_root,
+    serve,
     validate_repo_path,
 )
 import shutil
@@ -252,6 +256,77 @@ def test_git_show_initial_commit(test_repository):
     assert "test.txt" in result
 
 
+# Tests for resolve_repo_root (#3029)
+
+def test_resolve_repo_root_at_root(tmp_path: Path):
+    repo_path = tmp_path / "repo"
+    git.Repo.init(repo_path)
+    assert resolve_repo_root(repo_path).resolve() == repo_path.resolve()
+
+
+def test_resolve_repo_root_from_subdirectory(tmp_path: Path):
+    repo_path = tmp_path / "repo"
+    git.Repo.init(repo_path)
+    subdir = repo_path / "nested" / "deeper"
+    subdir.mkdir(parents=True)
+    assert resolve_repo_root(subdir).resolve() == repo_path.resolve()
+
+
+def test_resolve_repo_root_outside_any_repository(tmp_path: Path):
+    non_repo = tmp_path / "not_a_repo"
+    non_repo.mkdir()
+    with pytest.raises(git.InvalidGitRepositoryError):
+        resolve_repo_root(non_repo)
+
+
+def test_resolve_repo_root_dot_from_subdirectory(tmp_path: Path, monkeypatch):
+    # `--repository .` from a subdir should walk up to the repo root.
+    repo_path = tmp_path / "repo"
+    git.Repo.init(repo_path)
+    subdir = repo_path / "nested"
+    subdir.mkdir()
+    monkeypatch.chdir(subdir)
+    assert resolve_repo_root(Path(".")).resolve() == repo_path.resolve()
+
+
+class _StopServe(Exception):
+    pass
+
+
+def _fake_stdio_server():
+    raise _StopServe()
+
+
+def test_serve_resolves_subdirectory_at_startup(tmp_path: Path, monkeypatch, caplog):
+    repo_path = tmp_path / "repo"
+    git.Repo.init(repo_path)
+    subdir = repo_path / "nested"
+    subdir.mkdir()
+
+    monkeypatch.setattr("mcp_server_git.server.stdio_server", _fake_stdio_server)
+    caplog.set_level(logging.INFO, logger="mcp_server_git.server")
+
+    with pytest.raises(_StopServe):
+        asyncio.run(serve(subdir))
+
+    messages = [r.message for r in caplog.records]
+    assert any("Resolved --repository" in m and str(subdir) in m for m in messages)
+    assert any(f"Using repository at {repo_path}" in m for m in messages)
+
+
+def test_serve_rejects_path_outside_any_repository(tmp_path: Path, monkeypatch, caplog):
+    non_repo = tmp_path / "not_a_repo"
+    non_repo.mkdir()
+
+    monkeypatch.setattr("mcp_server_git.server.stdio_server", _fake_stdio_server)
+    caplog.set_level(logging.ERROR, logger="mcp_server_git.server")
+
+    asyncio.run(serve(non_repo))
+
+    messages = [r.message for r in caplog.records]
+    assert any("is not inside a Git repository" in m for m in messages)
+
+
 # Tests for validate_repo_path (repository scoping security fix)
 
 def test_validate_repo_path_no_restriction():