From 6728653f92457f0f9fc039ec03b1a0086e309c87 Mon Sep 17 00:00:00 2001
From: Cuarroc <47299143+Cuarroc@users.noreply.github.com>
Date: Fri, 9 Oct 2026 04:55:23 +0200
Subject: [PATCH] fix(review): resolve PR heads without shared FETCH_HEAD

Concurrent run-local.sh runs in one checkout overwrote FETCH_HEAD, so each
prompt could review the wrong PR. Fetch into refs/pa-review/pr-<n> and record
Head: in the prompt.

Test-First: scripts/test-review-local.sh::parallel PR fetches keep distinct diffs (no shared FETCH_HEAD)
Co-authored-by: Cursor <cursoragent@cursor.com>
---
 scripts/review/run-local.sh  | 17 ++++++++----
 scripts/test-review-local.sh | 54 ++++++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+), 5 deletions(-)

diff --git a/scripts/review/run-local.sh b/scripts/review/run-local.sh
index 8052b7ad..0a3737af 100755
--- a/scripts/review/run-local.sh
+++ b/scripts/review/run-local.sh
@@ -252,14 +252,19 @@ git -C "$TOP" rev-parse --verify --quiet "$base^{commit}" > /dev/null \
   || die 2 "Basis $base nicht gefunden (git fetch origin main?)."
 
 if [ -n "$pr" ]; then
-  git -C "$TOP" fetch --quiet origin "pull/$pr/head" 2> /dev/null \
-    || die 2 "PR $pr nicht gefunden: 'git fetch origin pull/$pr/head' schlug fehl (Nummer falsch, origin nicht erreichbar oder kein Zugriff)."
-  head_ref="$(git -C "$TOP" rev-parse FETCH_HEAD)" || die 2 "PR $pr: FETCH_HEAD nicht lesbar."
-  [ -n "$head_ref" ] || die 2 "PR $pr: FETCH_HEAD ist leer."
+  # Private ref per PR: concurrent runs in one checkout must not share FETCH_HEAD
+  # (a second fetch overwrites it before rev-parse). Force-update keeps the ref
+  # current when the same PR is reviewed again.
+  pr_ref="refs/pa-review/pr-$pr"
+  git -C "$TOP" fetch --quiet origin "+pull/$pr/head:$pr_ref" 2> /dev/null \
+    || die 2 "PR $pr nicht gefunden: 'git fetch origin +pull/$pr/head:$pr_ref' schlug fehl (Nummer falsch, origin nicht erreichbar oder kein Zugriff)."
+  head_ref="$(git -C "$TOP" rev-parse --verify "$pr_ref^{commit}")" \
+    || die 2 "PR $pr: Ref $pr_ref nicht lesbar."
+  [ -n "$head_ref" ] || die 2 "PR $pr: Ref $pr_ref ist leer."
   [ -n "$label" ] || label="pr$pr"
   subject="PR #$pr"
 else
-  head_ref="HEAD"
+  head_ref="$(git -C "$TOP" rev-parse --verify HEAD)" || die 2 "HEAD nicht lesbar."
   branch="$(git -C "$TOP" rev-parse --abbrev-ref HEAD 2> /dev/null)"
   if [ -z "$branch" ] || [ "$branch" = HEAD ]; then
     branch="head-$(git -C "$TOP" rev-parse --short HEAD)"
@@ -299,6 +304,8 @@ prompt_file="$out_dir/review_prompt_$label.md"
   cat << EOF
 # Review request $label: $subject against $base
 
+Head: $head_ref
+
 You are an independent reviewer (not the author${author:+; the author is a $author model}).
 Review the change below for correctness bugs, gaps, and safety regressions.
 Be concrete: cite file and line, say what breaks and when. Rate each finding
diff --git a/scripts/test-review-local.sh b/scripts/test-review-local.sh
index 1ac243df..a93c3285 100755
--- a/scripts/test-review-local.sh
+++ b/scripts/test-review-local.sh
@@ -450,6 +450,60 @@ else
   bad "kilo-Protokollname kollidiert: rc=$rc"; echo "$out"; ls "$tmp/k8" 2>&1
 fi
 
+# 14. Parallel PR fetches must not share FETCH_HEAD. A git wrapper overwrites
+#     FETCH_HEAD after a bare `pull/N/head` fetch (the old pattern); a private
+#     destination ref must keep each prompt on its own PR head.
+(
+  cd "$REPO" || exit 1
+  git checkout -q -b pr8-branch main
+  echo "MARKER_PR8_ONLY" > pr8.txt
+  git add pr8.txt && git commit -q -m pr8
+  git push -q origin HEAD:refs/pull/8/head
+  git checkout -q claude/demo-branch
+)
+sha7="$(git -C "$REPO" ls-remote origin refs/pull/7/head | awk '{print $1}')"
+sha8="$(git -C "$REPO" ls-remote origin refs/pull/8/head | awk '{print $1}')"
+REAL_GIT="$(command -v git)"
+mkdir -p "$tmp/bin-race"
+cat > "$tmp/bin-race/git" <<EOF
+#!/usr/bin/env bash
+REAL_GIT=$(printf '%q' "$REAL_GIT")
+joined="\$*"
+if [[ "\$joined" == *fetch* && "\$joined" =~ pull/([0-9]+)/head ]] \\
+  && [[ ! "\$joined" =~ pull/[0-9]+/head: ]]; then
+  "\$REAL_GIT" "\$@" || exit \$?
+  n="\${BASH_REMATCH[1]}"
+  other=8
+  [ "\$n" = 8 ] && other=7
+  if [ "\$1" = "-C" ]; then
+    "\$REAL_GIT" -C "\$2" fetch --quiet origin "pull/\$other/head"
+  else
+    "\$REAL_GIT" fetch --quiet origin "pull/\$other/head"
+  fi
+  exit \$?
+fi
+exec "\$REAL_GIT" "\$@"
+EOF
+chmod +x "$tmp/bin-race/git"
+run env PATH="$tmp/bin-race:$PATH" bash "$RUN" 7 --dry-run --models fake-a:cloud --out-dir "$tmp/race7"
+rc7=$rc; out7=$out
+run env PATH="$tmp/bin-race:$PATH" bash "$RUN" 8 --dry-run --models fake-a:cloud --out-dir "$tmp/race8"
+rc8=$rc; out8=$out
+if [ "$rc7" -eq 0 ] && [ "$rc8" -eq 0 ] \
+  && grep -q "MARKER_LINE two" "$tmp/race7/review_prompt_pr7.md" 2>/dev/null \
+  && ! grep -q "MARKER_PR8_ONLY" "$tmp/race7/review_prompt_pr7.md" 2>/dev/null \
+  && grep -q "MARKER_PR8_ONLY" "$tmp/race8/review_prompt_pr8.md" 2>/dev/null \
+  && ! grep -q "MARKER_LINE" "$tmp/race8/review_prompt_pr8.md" 2>/dev/null \
+  && grep -q "^Head: $sha7\$" "$tmp/race7/review_prompt_pr7.md" 2>/dev/null \
+  && grep -q "^Head: $sha8\$" "$tmp/race8/review_prompt_pr8.md" 2>/dev/null; then
+  ok "parallel PR fetches keep distinct diffs (no shared FETCH_HEAD)"
+else
+  bad "parallel PR FETCH_HEAD race: rc7=$rc7 rc8=$rc8"; echo "$out7"; echo "$out8"
+  ls "$tmp/race7" "$tmp/race8" 2>&1
+  head -n 8 "$tmp/race7/review_prompt_pr7.md" 2>&1
+  head -n 8 "$tmp/race8/review_prompt_pr8.md" 2>&1
+fi
+
 echo
 if [ "$fails" -eq 0 ]; then
   echo "test-review-local: alles gruen."