Bazel: fix lfs to do checkout rather than smudging

On Windows `git lfs smudge` was not working as expected.

misc/bazel/internal/git_lfs_checkout.py

@@ -0,0 +1,25 @@
+#!/usr/bin/env python3
+
+import sys
+import pathlib
+import subprocess
+import os
+
+sources = [pathlib.Path(arg).resolve() for arg in sys.argv[1:]]
+source_dir = pathlib.Path(os.path.commonpath(src.parent for src in sources))
+source_dir = subprocess.check_output(["git", "rev-parse", "--show-toplevel"], cwd=source_dir, text=True).strip()
+
+
+def is_lfs_pointer(file):
+    lfs_header = "version https://git-lfs.github.com/spec".encode()
+    with open(file, 'rb') as fileobj:
+        return fileobj.read(len(lfs_header)) == lfs_header
+
+
+for src in sources:
+    if is_lfs_pointer(src):
+        relative_src = src.relative_to(source_dir)
+        subprocess.run(["git", "lfs", "fetch", f"--include={relative_src}"], stdout=subprocess.DEVNULL, check=True,
+                       cwd=source_dir)
+        subprocess.run(["git", "lfs", "checkout", relative_src], check=True, cwd=source_dir)
+    pathlib.Path(src.name).symlink_to(src)

misc/bazel/internal/git_lfs_smudge.py

@@ -1,23 +0,0 @@
-#!/usr/bin/env python3
-
-import sys
-import pathlib
-import subprocess
-import os
-
-sources = [pathlib.Path(arg).resolve() for arg in sys.argv[1:]]
-source_dir = pathlib.Path(os.path.commonpath(src.parent for src in sources))
-
-def is_lfs_pointer(fileobj):
-    lfs_header = "version https://git-lfs.github.com/spec".encode()
-    actual_header = fileobj.read(len(lfs_header))
-    fileobj.seek(0)
-    return lfs_header == actual_header
-
-for src in sources:
-    with open(src, 'rb') as input:
-        if is_lfs_pointer(input):
-            with open(src.name, 'wb') as output:
-                subprocess.run(["git", "lfs", "smudge", "--", src], stdin=input, stdout=output, check=True, cwd=source_dir)
-            continue
-    pathlib.Path(src.name).symlink_to(src)

misc/bazel/lfs.bzl

@@ -1,13 +1,13 @@
 def lfs_smudge(repository_ctx, srcs):
     for src in srcs:
         repository_ctx.watch(src)
-    script = Label("//misc/bazel/internal:git_lfs_smudge.py")
+    script = Label("//misc/bazel/internal:git_lfs_checkout.py")
     python = repository_ctx.which("python3") or repository_ctx.which("python")
     if not python:
         fail("Neither python3 nor python executables found")
     res = repository_ctx.execute([python, script] + srcs, quiet = False)
     if res.return_code != 0:
-        fail("git LFS smudging failed while instantiating @%s:\n%s" % (repository_ctx.name, res.stderr))
+        fail("git LFS checkout failed while instantiating @%s:\n%s" % (repository_ctx.name, res.stderr))
 
 def _download_and_extract_lfs(repository_ctx):
     attr = repository_ctx.attr