Match odd and renamed paths in the vlt gate

`git diff --name-only` split on whitespace dropped paths with spaces,
quoted non-ASCII names, and reported only the new side of a rename, so a
vlt file changed that way next to an inert ci.yml edit could read as
"only ci.yml changed". Read NUL-separated paths with --no-renames and
test it against a scratch repository.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YVLGaJFexMvqCdiWxbiHXB

Author: claude

scripts/tests/test_vlt_compat_gate.py

@@ -4,6 +4,8 @@
 import contextlib
 import importlib.util
 import io
+import subprocess
+import tempfile
 import unittest
 from pathlib import Path
 
@@ -73,6 +75,66 @@ def test_no_base_runs(self):
         self.assertEqual(out.getvalue().split(), ["matrix=true"])
 
 
+class ChangedPaths(unittest.TestCase):
+    """main() on real commits: odd file names and renames still match."""
+
+    def commit_pair(self, before, after):
+        tmp = tempfile.TemporaryDirectory()
+        self.addCleanup(tmp.cleanup)
+        repo = Path(tmp.name)
+
+        def run(*args):
+            return subprocess.run(["git", *args], cwd=repo, check=True, capture_output=True,
+                                  text=True).stdout.strip()
+
+        def write(files):
+            for name, body in files.items():
+                path = repo / name
+                path.parent.mkdir(parents=True, exist_ok=True)
+                path.write_text(body, encoding="utf-8")
+
+        run("init", "-q")
+        run("config", "user.email", "t@example.com")
+        run("config", "user.name", "t")
+        write(before)
+        run("add", "-A")
+        run("commit", "-qm", "base")
+        base = run("rev-parse", "HEAD")
+        for name in [n for n in before if n not in after]:
+            run("rm", "-q", name)
+        write(after)
+        run("add", "-A")
+        run("commit", "-qm", "head")
+        return repo, base
+
+    def decide(self, before, after):
+        repo, base = self.commit_pair(before, after)
+        out = io.StringIO()
+        old_repo = gate.REPO
+        gate.REPO = repo
+        try:
+            with contextlib.redirect_stdout(out), contextlib.redirect_stderr(io.StringIO()):
+                gate.main(["--event", "pull_request", "--base", base])
+        finally:
+            gate.REPO = old_repo
+        return out.getvalue().split()
+
+    def base_tree(self):
+        return {CI_PATH: CI, "scripts/check-vlt-legs.py": "x\n"}
+
+    def test_inert_ci_yml_edit_skips(self):
+        after = dict(self.base_tree(), **{CI_PATH: CI + "\n# unrelated\n"})
+        self.assertEqual(self.decide(self.base_tree(), after), ["matrix=false"])
+
+    def test_odd_names_and_renames_still_run(self):
+        for name in ("crates/socket-patch-cli/tests/a vlt b.rs",
+                     "crates/socket-patch-cli/tests/\u00e9vlt.rs"):
+            after = dict(self.base_tree(), **{CI_PATH: CI + "\n# unrelated\n", name: "x\n"})
+            self.assertEqual(self.decide(self.base_tree(), after), ["matrix=true"], name)
+        moved = {CI_PATH: CI + "\n# unrelated\n", "scripts/elsewhere.py": "x\n"}
+        self.assertEqual(self.decide(self.base_tree(), moved), ["matrix=true"])
+
+
 class Workflow(unittest.TestCase):
     def test_heavy_jobs_wait_on_the_gate(self):
         for job in ("build", "plan"):

scripts/vlt-compat-gate.py

@@ -20,6 +20,7 @@
 
 ROOT = Path(__file__).resolve().parents[1]
 WORKFLOW = ROOT / ".github" / "workflows" / "vlt-compatibility.yml"
+REPO = ROOT  # where git runs; the tests point it at a scratch repository
 CI_PATH = ".github/workflows/ci.yml"
 
 
@@ -69,7 +70,7 @@ def ci_cells(text):
 
 
 def git(*args):
-    return subprocess.run(["git", *args], cwd=ROOT, capture_output=True, text=True, check=True).stdout
+    return subprocess.run(["git", *args], cwd=REPO, capture_output=True, text=True, check=True).stdout
 
 
 def needs_matrix(event, changed, filters, base_ci, head_ci):
@@ -92,7 +93,10 @@ def main(argv=None):
     matrix = True
     if args.event in ("pull_request", "push") and args.base:
         try:
-            changed = git("diff", "--name-only", args.base, args.head).split()
+            # NUL-separated paths are never quoted or split on spaces; with
+            # --no-renames a moved file lists both its old and new path.
+            out = git("diff", "-z", "--name-only", "--no-renames", args.base, args.head)
+            changed = [p for p in out.split("\0") if p]
             filters = event_paths(WORKFLOW.read_text(encoding="utf-8"), args.event)
             base_ci = git("show", f"{args.base}:{CI_PATH}")
             head_ci = git("show", f"{args.head}:{CI_PATH}")