Fix git checkout

Author: mdboom

bench_runner/git.py

@@ -2,6 +2,7 @@
 from __future__ import annotations
 
 
+import contextlib
 import datetime
 from pathlib import Path
 import shutil
@@ -137,23 +138,32 @@ def clone(
     url: str,
     *,
     branch: str | None = None,
-    depth: int | None = None,
+    depth: int = 1,
 ) -> None:
+    is_hash = re.match(r"^[0-9a-f]{40}$", branch) if branch else False
+
     dirname = Path(dirname)
     if dirname.is_dir():
-        if (
-            branch is not None
-            and re.match(r"^[0-9a-f]{40}$", branch)
-            and (dirname / ".git").is_dir()
-            and get_git_hash(dirname) == branch
-        ):
+        if is_hash and (dirname / ".git").is_dir() and get_git_hash(dirname) == branch:
             # This is a git repo, and the hash matches
             return
         shutil.rmtree(dirname)
 
-    args = ["git", "clone", url, str(dirname)]
-    if branch is not None:
-        args += ["--branch", branch]
-    if depth is not None:
-        args += ["--depth", str(depth)]
-    subprocess.check_call(args)
+    # Fetching a hash and fetching a branch require different approaches
+
+    if is_hash:
+        assert branch is not None
+        dirname.mkdir()
+        with contextlib.chdir(dirname):
+            subprocess.check_call(["git", "init"])
+            subprocess.check_call(["git", "remote", "add", "origin", url])
+            subprocess.check_call(
+                ["git", "fetch", "--depth", str(depth), "origin", branch]
+            )
+    else:
+        args = ["git", "clone", url, str(dirname)]
+        if branch is not None:
+            args += ["--branch", branch]
+        if depth is not None:
+            args += ["--depth", str(depth)]
+        subprocess.check_call(args)

bench_runner/util.py

@@ -1,5 +1,4 @@
 import functools
-import hashlib
 import itertools
 import os
 from pathlib import Path