Initial commit

Basic working code that is capable of establishing the Wireguard tunnel given that there is properly configured `.psk` file for at least one known wifi network (see README.md for more details)

preflight

@@ -0,0 +1,36 @@
+#! /bin/sh
+
+set -eu
+
+# Let's find out if a temporary build directory exists already
+BUILD_DIR=$(find . -type d -name "tmp*" -print -quit 2>/dev/null)
+
+# Create it if it doesn't
+if ! echo "$BUILD_DIR" | grep -q .; then
+  BUILD_DIR=$(mktemp --tmpdir=. --directory tmp.build.XXXXXXXXXX)
+fi
+
+# Preprocess the dotenv file
+./src/esh -o "$BUILD_DIR"/.env ./.env
+
+# Load the contents of the preprocessed dotenv file in order to
+# use the values for init stage below
+# https://www.shellcheck.net/wiki/SC1090
+# shellcheck source=/dev/null
+. "$BUILD_DIR"/.env
+
+echo "
+RELEASE_BASENAME=alpine-rpi-$ALPINE_VER_MAJOR.$ALPINE_VER_MINOR.$ALPINE_VER_PATCH-$ALPINE_ARCH
+RELEASE_VERSION=v$ALPINE_VER_MAJOR.$ALPINE_VER_MINOR
+ALPINE_DOCKER_IMAGE=alpine:$ALPINE_VER_MAJOR.$ALPINE_VER_MINOR.$ALPINE_VER_PATCH
+
+wlan0_cidr=$wlan0_base.0/24
+wlan0_address=$wlan0_base.1
+wlan0_range_start=$wlan0_base.2
+wlan0_range_end=$wlan0_base.254
+
+wg0_cidr=$wg0_base.0/24
+wg0_address=$wg0_base.12
+wg0_gateway=$wg0_base.1" >> "$BUILD_DIR"/.env
+
+echo "$BUILD_DIR"