lint: upgrade lint scripts for worktrees

Add a ci/lint.py script to run the linter both locally or inside the CI
(replacing .github/ci-lint-exec.py) which supports running from a
worktree.

Determines whether we are in a worktree, and mounts the real `.git`
directory as a read-only volume if we are.

ci/lint.py

@@ -0,0 +1,81 @@
+#!/usr/bin/env python3
+# Copyright (c) The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or https://opensource.org/license/mit/.
+
+import os
+import shlex
+import subprocess
+import sys
+import time
+from pathlib import Path
+
+
+def run(cmd, **kwargs):
+    print("+ " + shlex.join(cmd), flush=True)
+    kwargs.setdefault("check", True)
+    try:
+        return subprocess.run(cmd, **kwargs)
+    except Exception as e:
+        sys.exit(str(e))
+
+
+def get_worktree_mounts(repo_root):
+    git_path = repo_root / ".git"
+    if not git_path.is_file():
+        return []
+    content = git_path.read_text().strip()
+    if not content.startswith("gitdir: "):
+        return []
+    gitdir = (repo_root / content.removeprefix("gitdir: ")).resolve()
+    main_gitdir = gitdir.parent.parent
+    return [
+        f"--volume={gitdir}:{gitdir}",
+        f"--volume={main_gitdir}:{main_gitdir}:ro",
+    ]
+
+
+def main():
+    repo_root = Path(__file__).resolve().parent.parent
+    is_ci = os.environ.get("GITHUB_ACTIONS") == "true"
+    container = "bitcoin-linter"
+
+    build_cmd = [
+        "docker",
+        "buildx",
+        "build",
+        f"--tag={container}",
+        *shlex.split(os.environ.get("DOCKER_BUILD_CACHE_ARG", "")),
+        f"--file={repo_root}/ci/lint_imagefile",
+        str(repo_root),
+    ]
+    if run(build_cmd, check=False).returncode != 0:
+        if is_ci:
+            print("Retry building image after failure")
+            time.sleep(3)
+        run(build_cmd)
+
+    extra_env = []
+    if is_ci:
+        if os.environ.get("GITHUB_EVENT_NAME") == "pull_request":
+            extra_env = ["--env", "LINT_CI_IS_PR=1"]
+        elif os.environ.get("GITHUB_REPOSITORY") == "bitcoin/bitcoin":
+            extra_env = ["--env", "LINT_CI_SANITY_CHECK_COMMIT_SIG=1"]
+
+    run(
+        [
+            "docker",
+            "run",
+            "--rm",
+            *extra_env,
+            f"--volume={repo_root}:/bitcoin",
+            *get_worktree_mounts(repo_root),
+            *([] if is_ci else ["-it"]),
+            container,
+            *sys.argv[1:],
+        ]
+    )
+
+
+if __name__ == "__main__":
+    main()