deploy: USB update kit for the Pi and Jetson

pack-usb.sh writes the host part of the last commit and update.sh to a flash drive.
update.sh installs it over ~/Documents/radar_system, keeps configs, calibrations and
data, and leaves the previous version next to it as radar_system<N>.

deploy/pack-usb.sh

@@ -0,0 +1,45 @@
+#!/usr/bin/env bash
+# Put the project on a USB flash drive for deploy/update.sh: the host part of the
+# last commit as an archive (no venv, build, data or local configs) and the update
+# script, both in <drive>/radar_update/.
+#
+#     deploy/pack-usb.sh [DRIVE]
+#
+# DRIVE defaults to the only mounted removable drive.
+set -euo pipefail
+
+PROJECT_ROOT="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")/.." && pwd)"
+# What runs on the Pi or Jetson; device_firmware/ and docs/ stay on this machine.
+HOST_PATHS=(data_acq_and_processing deploy python_app run_config_examples Makefile
+            requirements.txt run_config.json start.sh locator_test_client.py)
+
+drive="${1:-}"
+if [[ -z "${drive}" ]]; then
+    mapfile -t drives < <(lsblk -nlo HOTPLUG,MOUNTPOINT | sed -n 's|^ *1 \+\(/.*\)$|\1|p')
+    if (( ${#drives[@]} != 1 )); then
+        echo "Found ${#drives[@]} mounted removable drives; name one: $0 /path/to/drive" >&2
+        printf '  %s\n' "${drives[@]}" >&2
+        exit 1
+    fi
+    drive="${drives[0]}"
+fi
+if [[ ! -d "${drive}" || ! -w "${drive}" ]]; then
+    echo "Not a writable directory: ${drive}" >&2
+    exit 1
+fi
+
+cd "${PROJECT_ROOT}"
+if [[ -n "$(git status --porcelain -- "${HOST_PATHS[@]}")" ]]; then
+    echo "Note: uncommitted changes are left out, the archive holds the last commit." >&2
+fi
+release="radar_system-$(git log -1 --format=%cd --date=format:%Y%m%d-%H%M)-$(git rev-parse --short HEAD)"
+out="${drive}/radar_update"
+mkdir -p "${out}"
+git archive --format=tar.gz --prefix=radar_system/ -o "${out}/${release}.tar.gz" HEAD "${HOST_PATHS[@]}"
+git show HEAD:deploy/update.sh > "${out}/update.sh"
+sync
+
+echo "Written to ${out}:"
+echo "  ${release}.tar.gz"
+echo "  update.sh"
+echo "On the device, from the drive's folder:  bash radar_update/update.sh"