Add book.sh initializing script

This script handles mdbook-admonish. See #2 for more info

Author: meator

.gitignore

@@ -1 +1,2 @@
 book
+cache

book.sh

@@ -0,0 +1,109 @@
+#!/bin/sh
+
+set +o errexit +o nounset
+
+get_asset_version() {
+	[ $# -ne 1 ] && return 1
+	asset_version="$(grep -o -m 1 -P '(?<=assets_version = ")[^"]*' "$1/book.toml")"
+}
+
+populate_cache() {
+	if ! type mdbook-admonish > /dev/null 2>&1; then
+		echo "\
+mdbook-admonish must be installed! See
+https://github.com/tommilligan/mdbook-admonish" 1>&2
+		exit 1
+	fi
+
+	[ $# -ne 1 ] && return 1
+
+	dir="$1"
+
+	mkdir -p "$dir"
+
+	# Create a fake mdbook config file so that mdbook-admonish can install its files
+	# to it.
+	touch "${dir}/book.toml"
+
+	mdbook-admonish install "$dir"
+
+	if ! [ -f "${dir}/mdbook-admonish.css" ]; then
+		echo "Couldn't generate ${dir}/mdbook-admonish.css!" 1>&2
+		exit 1
+	fi
+}
+
+exec_mdbook() {
+	[ $# -lt 2 ] && return 1
+	asset_version="$1"
+	finaldir="$2"
+	shift 2
+	exec env MDBOOK_PREPROCESSOR__ADMONISH="{\"assets_version\": \"$asset_version\"}"\
+	 MDBOOK_OUTPUT__HTML__ADDITIONAL_CSS="[\"${finaldir}/mdbook-admonish.css\"]"\
+	 mdbook "$@"
+}
+
+usage="\
+A wrapper for mdBook which handles mdbook-admonish.
+
+$0 needs to generate some files. It puts them to <the directory the script
+resides in>/cache/ by default.
+
+You can change the base directory with -b <directory> (directory the script
+resides in by default) and the cache subdirectory (cache/ by default) with -c
+<directory relative to base directory>. The files are put into <base
+directory>/<subdirectory>
+
+Directories are created if they do not exist.
+
+Usage:
+  $0 [-b <directory>] [-c <directory>] mdbook commandline...
+  $0 -h
+
+Options:
+  -h              Show this help message.
+  -b=<directory>  Set base directory.
+  -c=<directory>  Set cache directory.
+
+Example usage:
+  Build the book (calls \`mdbook build\` internally):
+    $0 build
+  Serve the book (calls \`mdbook serve\` internally):
+    $0 serve
+"
+
+# I assume $0 is set and it's valid.
+basedir="$(dirname $0)"
+cachedir="cache/"
+
+while getopts hb:c: f; do
+	case $f in
+	h)
+		printf %s "$usage"
+		exit 0
+		;;
+	b)
+		basedir="$OPTARG"
+		;;
+	c)
+		cachedir="$OPTARG"
+		;;
+	*)
+		printf %s "$usage"
+		exit 1
+		;;
+	esac
+done
+
+shift $((OPTIND - 1))
+
+finaldir="${basedir}/${cachedir}"
+
+if [ -f "${finaldir}/mdbook-admonish.css" ]; then
+	get_asset_version "$finaldir"
+	exec_mdbook "$asset_version" "$finaldir" "$@"
+else
+	populate_cache "$finaldir"
+	get_asset_version "$finaldir"
+	exec_mdbook "$asset_version" "$finaldir" "$@"
+fi