From 5ebc144f828b24156fe18dbb34eeb1fa2ab17ec1 Mon Sep 17 00:00:00 2001
From: Evan Rusackas <evan@preset.io>
Date: Fri, 17 Jul 2026 17:41:12 -0700
Subject: [PATCH] fix(ci): diff pre-commit changed files against the live base,
 cap the env payload
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github.event.pull_request.base.sha is frozen at PR creation, so the
changed-files detection on a long-lived PR diffs against the original
branch point and picks up all of master's churn since then. This week
that list crossed the kernel's per-env-var size limit (MAX_ARG_STRLEN),
killing the pre-commit step with "Argument list too long" before bash
could start — observed on #41127, where the frozen base predated the
antd v6 upgrade and the i18n catalog canonicalization.

Diff against HEAD^1 instead: HEAD is the PR merge commit, so its first
parent is the current base-branch tip and the diff is exactly the PR's
own files. Also fall back to --all-files when the computed list exceeds
100KB, so a PR that legitimately touches thousands of files degrades to
a full sweep instead of an unstartable step.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
---
 .github/workflows/pre-commit.yml | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/pre-commit.yml b/.github/workflows/pre-commit.yml
index 11ad48f4b3e..ab95614b8a5 100644
--- a/.github/workflows/pre-commit.yml
+++ b/.github/workflows/pre-commit.yml
@@ -81,7 +81,6 @@ jobs:
         id: changed_files
         env:
           EVENT_NAME: ${{ github.event_name }}
-          BASE_SHA: ${{ github.event.pull_request.base.sha }}
           BEFORE_SHA: ${{ github.event.before }}
         run: |
           set -euo pipefail
@@ -95,7 +94,15 @@ jobs:
           # Resolve the commit to diff against.
           base=""
           if [ "${EVENT_NAME}" = "pull_request" ]; then
-            base="${BASE_SHA}"
+            # HEAD is the PR merge commit, so its first parent is the current
+            # tip of the base branch. github.event.pull_request.base.sha is
+            # NOT that: GitHub freezes it at PR creation, so on a long-lived
+            # PR it points at the original branch point and the diff picks up
+            # all of the base branch's churn since then — thousands of paths,
+            # enough for the CHANGED_FILES env var below to exceed the
+            # kernel's per-variable size limit and kill the step with
+            # "Argument list too long" before bash even starts.
+            base="$(git rev-parse HEAD^1 2>/dev/null || true)"
           elif [ -n "${BEFORE_SHA:-}" ] && \
                [ "${BEFORE_SHA}" != "0000000000000000000000000000000000000000" ]; then
             base="${BEFORE_SHA}"
@@ -114,6 +121,15 @@ jobs:
           # Files present in HEAD that changed since the base (drop deletions).
           files="$(git diff --name-only --diff-filter=ACMRT "${base}...HEAD")"
 
+          # Env vars have a hard per-variable size limit (E2BIG at step
+          # start). A PR that legitimately touches thousands of files is
+          # better served by --all-files anyway.
+          if [ "$(printf '%s' "${files}" | wc -c)" -gt 100000 ]; then
+            echo "::notice::Changed-file list too large to pass via env; falling back to --all-files."
+            echo "mode=all" >> "$GITHUB_OUTPUT"
+            exit 0
+          fi
+
           if [ -z "${files}" ]; then
             echo "mode=none" >> "$GITHUB_OUTPUT"
           else