Merge branch 'install-hugo-on-windows'

There is a script to install Hugo on Unix-like systems, with the
improvable name `upgrade-hugo.sh`. This topic branch renames it, and
also allows people like me who are not in the "I don't do Windows" camp
to benefit from this script, too. It _does_ assume to be run in a Git
Bash when run on Windows.

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

Author: dscho

script/install-hugo.sh

@@ -0,0 +1,32 @@
+#!/bin/sh
+
+die() {
+    echo "$*" >&2
+    exit 1
+}
+
+case "$MSYSTEM" in
+MINGW64)
+	suffix=_windows-amd64.zip
+	update() {
+		unzip -d $HOME/bin /tmp/hugo$suffix hugo.exe
+	}
+	;;
+*)
+	suffix=_linux-amd64.deb
+	update() {
+		sudo dpkg -i /tmp/hugo$suffix
+	}
+	;;
+esac
+
+HUGO_VERSION=$(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$suffix $download_url/v$HUGO_VERSION/hugo_extended_${HUGO_VERSION}${suffix} &&
+update ||
+die "Failed to install Hugo version $HUGO_VERSION"