Fix patches on Windows

.gitattributes

@@ -0,0 +1,2 @@
+# Patches must retain LF even when Git for Windows enables core.autocrlf.
+*.patch text eol=lf

.github/workflows/build.yml

@@ -187,6 +187,7 @@ jobs:
         shell: bash
         run: |
           set -euo pipefail
+          python3 tests/test-patch-checkout.py
           for patch in patches/*.patch; do
             git -C build/angle apply --check "$GITHUB_WORKSPACE/$patch"
             git -C build/angle apply "$GITHUB_WORKSPACE/$patch"

scripts/build-windows.ps1

@@ -208,6 +208,8 @@ try {
           continue
         }
 
+        # Repeat the failed check without suppressing Git's hunk diagnostics.
+        git apply --check $patch.FullName
         throw "Patch does not apply cleanly: $($patch.FullName)"
       }
     }

tests/test-patch-checkout.py

@@ -0,0 +1,52 @@
+#!/usr/bin/env python3
+"""Check Windows-style patch checkout and apply against the pinned ANGLE tree."""
+import os
+from pathlib import Path
+import subprocess
+import tempfile
+
+ROOT = Path(__file__).resolve().parents[1]
+ANGLE = Path(os.environ.get("ANGLE_DIR", str(ROOT / "build/angle")))
+PIN = (ROOT / "ANGLE_COMMIT").read_text().strip()
+
+
+def git(*args, cwd):
+    return subprocess.check_output(["git", *args], cwd=cwd)
+
+
+with tempfile.TemporaryDirectory(prefix="angle-patch-checkout-") as tmp:
+    tmp = Path(tmp)
+    patch_repo = tmp / "patches"
+    patch_repo.mkdir()
+    git("init", "-q", cwd=patch_repo)
+    # Copy only the inputs to a disposable repo so no real index/config is changed.
+    (patch_repo / ".gitattributes").write_bytes((ROOT / ".gitattributes").read_bytes())
+    for patch in sorted((ROOT / "patches").glob("*.patch")):
+        (patch_repo / patch.name).write_bytes(patch.read_bytes())
+    git("add", ".", cwd=patch_repo)
+
+    for autocrlf in ("false", "true"):
+        checkout = tmp / ("checkout-" + autocrlf)
+        checkout.mkdir()
+        git("-c", "core.autocrlf=" + autocrlf, "checkout-index", "--all",
+            "--prefix=" + str(checkout) + "/", cwd=patch_repo)
+        sources = tmp / ("sources-" + autocrlf)
+        sources.mkdir()
+        git("init", "-q", cwd=sources)
+        patches = sorted(checkout.glob("*.patch"))
+        assert patches, "No patches found"
+        for patch in patches:
+            data = patch.read_bytes()
+            assert b"\r\n" not in data, f"{patch.name} checked out with CRLF"
+            for line in data.decode().splitlines():
+                if line.startswith("--- a/"):
+                    name = line[6:]
+                    dest = sources / name
+                    if not dest.exists():
+                        dest.parent.mkdir(parents=True, exist_ok=True)
+                        dest.write_bytes(git("show", PIN + ":" + name, cwd=ANGLE))
+        for patch in patches:
+            git("apply", "--check", str(patch), cwd=sources)
+            git("apply", str(patch), cwd=sources)
+            git("apply", "--reverse", "--check", str(patch), cwd=sources)
+        print(f"PASS: core.autocrlf={autocrlf}: LF checkout and all patches apply")