Lift drill into evals/ at 013fcb8b7dbefd6d3fa4653493e5d2ec8e7f985b

rsync of obra/drill@013fcb8b7d into superpowers/evals/, excluding
.git/, .venv/, results/, .env/, __pycache__/, *.egg-info/,
.private-journal/.

The drill repo is unaffected by this commit; archival is a separate
manual step after this PR merges.

Source SHA recorded at evals/.drill-source-sha for divergence
detection.

evals/setup_helpers/base.py

@@ -0,0 +1,63 @@
+from __future__ import annotations
+import shutil
+import subprocess
+from pathlib import Path
+
+
+def _git(args: list[str], cwd: Path, **kwargs) -> subprocess.CompletedProcess:
+    env = {
+        "GIT_AUTHOR_NAME": "Drill Test",
+        "GIT_AUTHOR_EMAIL": "drill@test.local",
+        "GIT_COMMITTER_NAME": "Drill Test",
+        "GIT_COMMITTER_EMAIL": "drill@test.local",
+        **__import__("os").environ,
+    }
+    return subprocess.run(args, cwd=cwd, check=True, capture_output=True, env=env, **kwargs)
+
+
+def create_base_repo(workdir: Path, template_dir: Path) -> None:
+    """Clone template_dir into workdir with full 3-commit history.
+
+    If template_dir has a .git, clone it directly.  Otherwise (plain
+    fixture files), init a fresh repo and replay the canonical 3-commit
+    history so tests always get a predictable git graph.
+    """
+    workdir = Path(workdir)
+    template_dir = Path(template_dir)
+
+    if (template_dir / ".git").exists():
+        subprocess.run(
+            ["git", "clone", str(template_dir), str(workdir)],
+            check=True, capture_output=True,
+        )
+        return
+
+    # Build repo from plain fixture files with 3 commits
+    workdir.mkdir(parents=True, exist_ok=True)
+    _git(["git", "init", "-b", "main"], cwd=workdir)
+    _git(["git", "config", "user.email", "drill@test.local"], cwd=workdir)
+    _git(["git", "config", "user.name", "Drill Test"], cwd=workdir)
+
+    # Commit 1: package.json + README.md
+    for name in ("package.json", "README.md"):
+        src = template_dir / name
+        if src.exists():
+            shutil.copy2(src, workdir / name)
+    _git(["git", "add", "package.json", "README.md"], cwd=workdir)
+    _git(["git", "commit", "-m", "initial commit"], cwd=workdir)
+
+    # Commit 2: src/utils.js
+    src_dir = workdir / "src"
+    src_dir.mkdir(exist_ok=True)
+    utils_src = template_dir / "src" / "utils.js"
+    if utils_src.exists():
+        shutil.copy2(utils_src, src_dir / "utils.js")
+    _git(["git", "add", "src/utils.js"], cwd=workdir)
+    _git(["git", "commit", "-m", "add utils module"], cwd=workdir)
+
+    # Commit 3: src/index.js
+    index_src = template_dir / "src" / "index.js"
+    if index_src.exists():
+        shutil.copy2(index_src, src_dir / "index.js")
+    _git(["git", "add", "src/index.js"], cwd=workdir)
+    _git(["git", "commit", "-m", "add entry point"], cwd=workdir)