ci: fetch the ADR citation check from .github instead of keeping a copy

.github/workflows/main.yml

@@ -15,6 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v6
+      - uses: extractions/setup-just@v4
       - uses: astral-sh/setup-uv@v8.2.0
       - run: uv python install 3.14
       - run: uv python pin 3.14
@@ -23,6 +24,7 @@ jobs:
           uv run ruff format . --check
           uv run ruff check . --no-fix
           uv run ty check
+      - run: just adr-check
 
   pytest:
     runs-on: ubuntu-latest

justfile

@@ -34,3 +34,14 @@ lint:
     uv run ruff format .
     uv run ruff check . --fix
     uv run ty check
+
+adr_check_source := "https://raw.githubusercontent.com/modern-python/.github/main/tests/test_adr_citations.py"
+
+# Tracks main on purpose: the shared check is unpinned.
+adr-check:
+    #!/usr/bin/env sh
+    set -eu
+    dir="$(mktemp -d .adr-check.XXXXXX)"
+    trap 'rm -rf "$dir"' EXIT
+    curl -fsSL "{{ adr_check_source }}" -o "$dir/test_adr_citations.py"
+    uv run --no-sync pytest --rootdir=. --noconftest -o addopts= "$dir/test_adr_citations.py"