Overture download script [#571]

* add bash help text
* query for latest Overture release from STAC catalog

Author: bdon

tiles/download-overture.sh

@@ -1,9 +1,45 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
-REL="${1:-2026-02-18.0}"
-BBOX="${2:-7.408446,43.722901,7.4405,43.752481}"
-OUT="data/sources/${3:-monaco.parquet}"
+STAC_CATALOG="https://stac.overturemaps.org/catalog.json"
+DEFAULT_BBOX="7.408446,43.722901,7.4405,43.752481"
+DEFAULT_OUT="data/sources/monaco.parquet"
+
+usage() {
+  cat <<EOF
+Usage: $0 [RELEASE] [BBOX] [OUTPUT]
+
+Downloads Overture Maps data for a bounding box as a Parquet file.
+
+Arguments:
+  RELEASE  Overture release version         (default: latest, from ${STAC_CATALOG})
+  BBOX     xmin,ymin,xmax,ymax in WGS84     (default: ${DEFAULT_BBOX})
+  OUTPUT   Output file path                 (default: ${DEFAULT_OUT})
+
+Example:
+  $0 2026-06-17.0 -122.52,37.70,-122.35,37.83 data/sources/sf.parquet
+EOF
+}
+
+latest_release() {
+  # A network failure yields empty output rather than aborting under `set -e`,
+  # so the caller can report it.
+  duckdb -noheader -list -c \
+    "SELECT latest FROM read_json('${STAC_CATALOG}')" 2>/dev/null || true
+}
+
+if [[ "${1:-}" == "--help" || "${1:-}" == "-h" ]]; then
+  usage
+  exit 0
+fi
+
+REL="${1:-$(latest_release)}"
+if [[ -z "$REL" ]]; then
+  echo "Could not determine the latest release from ${STAC_CATALOG}; pass one explicitly." >&2
+  exit 1
+fi
+BBOX="${2:-$DEFAULT_BBOX}"
+OUT="${3:-$DEFAULT_OUT}"
 
 IFS=',' read -r XMIN YMIN XMAX YMAX <<< "$BBOX"