Add a precommit hook to automatically update .ci/docker/ci_commit_pins/pytorch.txt when torch_pin.py is changed. (#15072)

This pull request introduces a new script,
`.github/scripts/update_pytorch_pin.py`, which automates the process of
updating the PyTorch commit pin based on the nightly version specified
in `torch_pin.py`. The script parses the nightly version, fetches the
corresponding commit hash from the PyTorch nightly branch using the
GitHub API, and updates the pin file accordingly. This automation helps
ensure that the CI environment uses the correct nightly commit for
PyTorch.

Automation of PyTorch nightly pin updating:

* Added `.github/scripts/update_pytorch_pin.py`, a script that reads the
nightly version from `torch_pin.py`, parses the date, fetches the
corresponding commit hash from the PyTorch nightly branch via the GitHub
API, and updates `.ci/docker/ci_commit_pins/pytorch.txt` with the new
hash.

Test plan:

Run `.githooks/install.sh`
Tested manually by changing `NIGHTLY_VERSION` and try to commit locally.
Was able to see `.ci/docker/ci_commit_pins/pytorch.txt` being updated.

Author: larryliu0820

.githooks/README.md

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+# Git Hooks
+
+This directory contains Git hooks for the ExecuTorch repository.
+
+## Pre-commit Hook
+
+The pre-commit hook automatically updates the PyTorch commit pin in `.ci/docker/ci_commit_pins/pytorch.txt` whenever `torch_pin.py` is modified.
+
+### How It Works
+
+1. When you commit changes to `torch_pin.py`, the hook detects the change
+2. It parses the `NIGHTLY_VERSION` field (e.g., `dev20251004`)
+3. Converts it to a date string (e.g., `2025-10-04`)
+4. Fetches the corresponding commit hash from the PyTorch nightly branch at https://github.com/pytorch/pytorch/tree/nightly
+5. Updates `.ci/docker/ci_commit_pins/pytorch.txt` with the new commit hash
+6. Automatically stages the updated file for commit
+
+### Installation
+
+To install the Git hooks, run:
+
+```bash
+.githooks/install.sh
+```
+
+This will copy the pre-commit hook to `.git/hooks/` and make it executable.
+
+### Manual Usage
+
+You can also run the update script manually at any time:
+
+```bash
+python .github/scripts/update_pytorch_pin.py
+```
+
+### Uninstalling
+
+To remove the pre-commit hook:
+
+```bash
+rm .git/hooks/pre-commit
+```
+
+## Troubleshooting
+
+If the hook fails during a commit:
+
+1. Check that Python 3 is available in your PATH
+2. Ensure you have internet connectivity to fetch commits from GitHub
+3. Verify that the `NIGHTLY_VERSION` in `torch_pin.py` is in the correct format (`devYYYYMMDD`)
+4. Make sure the corresponding nightly release exists in the PyTorch nightly branch
+
+You can run the script manually to see detailed error messages:
+
+```bash
+python .github/scripts/update_pytorch_pin.py
+```

.githooks/install.sh

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+#!/usr/bin/env bash
+
+# Script to install Git hooks from .githooks directory
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+GIT_DIR="$(git rev-parse --git-dir)"
+HOOKS_DIR="${GIT_DIR}/hooks"
+
+echo "Installing Git hooks..."
+
+# Install pre-commit hook
+echo "📦 Installing pre-commit hook..."
+cp "${SCRIPT_DIR}/pre-commit" "${HOOKS_DIR}/pre-commit"
+chmod +x "${HOOKS_DIR}/pre-commit"
+echo "✅ pre-commit hook installed"
+
+echo ""
+echo "🎉 Git hooks installed successfully!"
+echo ""
+echo "The pre-commit hook will automatically update .ci/docker/ci_commit_pins/pytorch.txt"
+echo "whenever you commit changes to torch_pin.py"

.githooks/pre-commit

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+#!/usr/bin/env bash
+
+# Pre-commit hook to automatically update PyTorch commit pin when torch_pin.py changes
+
+# Check if torch_pin.py is being committed
+if git diff --cached --name-only | grep -q "^torch_pin.py$"; then
+    echo "🔍 Detected changes to torch_pin.py"
+    echo "📝 Updating PyTorch commit pin..."
+
+    # Run the update script
+    if python .github/scripts/update_pytorch_pin.py; then
+        # Check if pytorch.txt was modified
+        if ! git diff --quiet .ci/docker/ci_commit_pins/pytorch.txt; then
+            echo "✅ PyTorch commit pin updated successfully"
+            # Stage the updated file
+            git add .ci/docker/ci_commit_pins/pytorch.txt
+            echo "📌 Staged .ci/docker/ci_commit_pins/pytorch.txt"
+        else
+            echo "ℹ️  PyTorch commit pin unchanged"
+        fi
+    else
+        echo "❌ Failed to update PyTorch commit pin"
+        echo "Please run: python .github/scripts/update_pytorch_pin.py"
+        exit 1
+    fi
+fi
+
+exit 0

.github/scripts/update_pytorch_pin.py

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+#!/usr/bin/env python3
+
+import json
+import re
+import sys
+import urllib.request
+from datetime import datetime
+
+
+def parse_nightly_version(nightly_version):
+    """
+    Parse NIGHTLY_VERSION (e.g., 'dev20251004') to date string (e.g., '2025-10-04').
+
+    Args:
+        nightly_version: String in format 'devYYYYMMDD'
+
+    Returns:
+        Date string in format 'YYYY-MM-DD'
+    """
+    match = re.match(r"dev(\d{4})(\d{2})(\d{2})", nightly_version)
+    if not match:
+        raise ValueError(f"Invalid NIGHTLY_VERSION format: {nightly_version}")
+
+    year, month, day = match.groups()
+    return f"{year}-{month}-{day}"
+
+
+def get_torch_nightly_version():
+    """
+    Read NIGHTLY_VERSION from torch_pin.py.
+
+    Returns:
+        NIGHTLY_VERSION string
+    """
+    with open("torch_pin.py", "r") as f:
+        content = f.read()
+
+    match = re.search(r'NIGHTLY_VERSION\s*=\s*["\']([^"\']+)["\']', content)
+    if not match:
+        raise ValueError("Could not find NIGHTLY_VERSION in torch_pin.py")
+
+    return match.group(1)
+
+
+def get_commit_hash_for_nightly(date_str):
+    """
+    Fetch commit hash from PyTorch nightly branch for a given date.
+
+    Args:
+        date_str: Date string in format 'YYYY-MM-DD'
+
+    Returns:
+        Commit hash string
+    """
+    api_url = "https://api.github.com/repos/pytorch/pytorch/commits"
+    params = f"?sha=nightly&per_page=100"
+    url = api_url + params
+
+    req = urllib.request.Request(url)
+    req.add_header("Accept", "application/vnd.github.v3+json")
+    req.add_header("User-Agent", "ExecuTorch-Bot")
+
+    try:
+        with urllib.request.urlopen(req) as response:
+            commits = json.loads(response.read().decode())
+    except Exception as e:
+        print(f"Error fetching commits: {e}", file=sys.stderr)
+        sys.exit(1)
+
+    # Look for commit with title matching "{date_str} nightly release"
+    target_title = f"{date_str} nightly release"
+
+    for commit in commits:
+        commit_msg = commit.get("commit", {}).get("message", "")
+        # Check if the first line of commit message matches
+        first_line = commit_msg.split("\n")[0].strip()
+        if first_line == target_title or first_line.startswith(f"{date_str} nightly"):
+            return commit["sha"]
+
+    raise ValueError(
+        f"Could not find commit with title matching '{target_title}' in nightly branch"
+    )
+
+
+def update_pytorch_pin(commit_hash):
+    """
+    Update .ci/docker/ci_commit_pins/pytorch.txt with the new commit hash.
+
+    Args:
+        commit_hash: Commit hash to write
+    """
+    pin_file = ".ci/docker/ci_commit_pins/pytorch.txt"
+    with open(pin_file, "w") as f:
+        f.write(f"{commit_hash}\n")
+    print(f"Updated {pin_file} with commit hash: {commit_hash}")
+
+
+def main():
+    try:
+        # Read NIGHTLY_VERSION from torch_pin.py
+        nightly_version = get_torch_nightly_version()
+        print(f"Found NIGHTLY_VERSION: {nightly_version}")
+
+        # Parse to date string
+        date_str = parse_nightly_version(nightly_version)
+        print(f"Parsed date: {date_str}")
+
+        # Fetch commit hash from PyTorch nightly branch
+        commit_hash = get_commit_hash_for_nightly(date_str)
+        print(f"Found commit hash: {commit_hash}")
+
+        # Update the pin file
+        update_pytorch_pin(commit_hash)
+
+        print("Successfully updated PyTorch commit pin!")
+
+    except Exception as e:
+        print(f"Error: {e}", file=sys.stderr)
+        sys.exit(1)
+
+
+if __name__ == "__main__":
+    main()