Add frontmatter date auto-update script and pre-commit hook (#639)

Create tools/update-dates.py that keeps Hugo frontmatter date: fields
current. Runs as a git pre-commit hook (default) or in batch mode.

Features:
- Updates existing date: fields to current timestamp
- Adds date: field to files that have frontmatter but no date
- Skips files without YAML frontmatter
- Preserves CRLF/LF line endings across platforms
- Handles UTF-8 BOM files (strips BOM on decode)
- Handles quoted date values in YAML
- Auto-re-stages updated files in pre-commit mode
- --dry-run and --verbose flags for safe previewing
- Zero external dependencies (Python 3.8+ stdlib only)

Also includes:
- tools/README.md with usage documentation
- tools/install-hooks.sh (bash) and install-hooks.ps1 (PowerShell)
  install scripts with existing-hook detection and python3 fallback

Tested against all 1216 content .md files with 0 errors.

Co-authored-by: Beatris Mendez Gandica <bemendez@microsoft.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: 3 people

tools/README.md

@@ -0,0 +1,66 @@
+# tools/ — Workshop development utilities
+
+Scripts to help contributors maintain the NuevoFoundation workshops repo.
+
+## update-dates.py
+
+Keeps Hugo frontmatter `date:` fields current. When you commit a markdown
+file, the date updates automatically so readers know when content last changed.
+
+### Quick start (pre-commit hook)
+
+Install once — all future commits auto-update dates:
+
+```bash
+# Linux / macOS / Git Bash
+bash tools/install-hooks.sh
+
+# Windows PowerShell
+.\tools\install-hooks.ps1
+```
+
+Then just commit normally. Any staged `.md` file gets its `date:` field
+updated to the current timestamp before the commit completes.
+
+### Manual usage
+
+```bash
+# See what would change (staged files)
+python tools/update-dates.py --dry-run
+
+# Update all .md files under a path
+python tools/update-dates.py --all content/english/python-basics/
+
+# Verbose output
+python tools/update-dates.py --verbose --dry-run
+```
+
+### How it works
+
+1. Finds `.md` files (staged files by default, or `--all <path>` for batch)
+2. Parses YAML frontmatter (the `---` block at the top of each file)
+3. Updates the `date:` field to the current timestamp
+4. If a file has frontmatter but no `date:` field, one is added
+5. Files without frontmatter are skipped
+6. In pre-commit mode, updated files are re-staged automatically
+
+### Flags
+
+| Flag | Description |
+|------|-------------|
+| `--all PATH` | Batch mode: update all `.md` files under PATH |
+| `--dry-run` | Show what would change without writing |
+| `--verbose` / `-v` | Print each file and its status |
+
+### Date format
+
+Matches the existing Hugo frontmatter format:
+
+```yaml
+date: 2026-04-26T21:23:39-07:00
+```
+
+### Requirements
+
+- Python 3.8+
+- No external dependencies (stdlib only)

tools/install-hooks.ps1

@@ -0,0 +1,48 @@
+# Install update-dates.py as a git pre-commit hook (Windows).
+# Run from the repo root: .\tools\install-hooks.ps1
+
+$ErrorActionPreference = "Stop"
+
+$hook = ".git\hooks\pre-commit"
+$script = "tools\update-dates.py"
+
+if (-not (Test-Path $script)) {
+    Write-Error "Run this from the repo root (cannot find $script)"
+    exit 1
+}
+
+if (Test-Path $hook) {
+    Write-Warning "$hook already exists:"
+    Get-Content $hook
+    $answer = Read-Host "Overwrite? [y/N]"
+    if ($answer -notin @("y", "Y")) {
+        Write-Host "Aborted."
+        exit 0
+    }
+}
+
+if (-not (Test-Path ".git\hooks")) {
+    New-Item -ItemType Directory -Path ".git\hooks" -Force | Out-Null
+}
+
+$hookContent = @"
+#!/usr/bin/env bash
+# Pre-commit hook: update frontmatter dates on staged .md files
+if command -v python3 &>/dev/null; then
+    python3 tools/update-dates.py
+elif command -v python &>/dev/null; then
+    python tools/update-dates.py
+else
+    echo "Warning: python not found, skipping date update" >&2
+fi
+"@
+
+# Write UTF-8 without BOM to avoid breaking the shebang line
+$resolvedHook = Join-Path (Resolve-Path ".").Path $hook
+[System.IO.File]::WriteAllText(
+    $resolvedHook,
+    $hookContent,
+    [System.Text.UTF8Encoding]::new($false)
+)
+
+Write-Host "Installed pre-commit hook at $hook"

tools/install-hooks.sh

@@ -0,0 +1,42 @@
+#!/usr/bin/env bash
+# Install update-dates.py as a git pre-commit hook.
+# Run from the repo root: bash tools/install-hooks.sh
+
+set -e
+
+HOOK=".git/hooks/pre-commit"
+SCRIPT="tools/update-dates.py"
+
+if [ ! -f "$SCRIPT" ]; then
+    echo "Error: run this from the repo root (cannot find $SCRIPT)"
+    exit 1
+fi
+
+if [ -f "$HOOK" ]; then
+    echo "Warning: $HOOK already exists."
+    echo "Existing content:"
+    cat "$HOOK"
+    echo ""
+    read -p "Overwrite? [y/N] " answer
+    if [ "$answer" != "y" ] && [ "$answer" != "Y" ]; then
+        echo "Aborted."
+        exit 0
+    fi
+fi
+
+mkdir -p .git/hooks
+
+cat > "$HOOK" << 'EOF'
+#!/usr/bin/env bash
+# Pre-commit hook: update frontmatter dates on staged .md files
+if command -v python3 &>/dev/null; then
+    python3 tools/update-dates.py
+elif command -v python &>/dev/null; then
+    python tools/update-dates.py
+else
+    echo "Warning: python not found, skipping date update" >&2
+fi
+EOF
+
+chmod +x "$HOOK"
+echo "Installed pre-commit hook at $HOOK"