Add a script to upgrade Hugo locally to the recorded version

This script currently only works on Linux. If need be, it can be
extended to cover other operating systems. That will be the
responsibility of people who want that support, though.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

script/upgrade-hugo.sh

@@ -0,0 +1,17 @@
+#!/bin/sh
+
+die() {
+    echo "$*" >&2
+    exit 1
+}
+
+HUGO_VERSION=$(sed -n 's/^ *hugo_version: *//p' <hugo.yml) &&
+test -n "$HUGO_VERSION" ||
+die "hugo_version not found in hugo.yml"
+
+echo "Upgrading to Hugo v${HUGO_VERSION}" >&2
+
+download_url=https://github.com/gohugoio/hugo/releases/download &&
+curl -Lo /tmp/hugo.deb $download_url/v$HUGO_VERSION/hugo_extended_${HUGO_VERSION}_linux-amd64.deb &&
+sudo dpkg -i /tmp/hugo.deb ||
+die "Failed to install Hugo version $HUGO_VERSION"