Translate help links using a pandoc Lua filter instead of sed

Using a pandoc filter is more reliable - it ensures that only links
are rewritten, and not other parts of the text that look like a link
but aren't actually one.

help.sh

@@ -12,15 +12,12 @@ convert_single() {
 	echo "Converting ${file} to ${format} (.${extension})..."
 
 	rm -f "${file}.${extension}"
-	pandoc "${file}" -f markdown_github -t "${format}" -s | sed "s/\.md/.${extension}/g" > "${file%.md}.${extension}"
+	pandoc "${file}" -f markdown_github -t "${format}" --lua-filter pandoc_links_to_html.lua -o "${file%.md}.${extension}"
 }
 
 if ! which pandoc &> /dev/null; then
 	echo "pandoc is not installed. Aborting..."
 	exit 1
-elif ! which sed &> /dev/null; then
-	echo "sed is not installed. Aborting..."
-	exit 1
 fi
 
 find src/main/resources/help -name "*.md" -print0 | while IFS="" read -r -d "" file; do

pandoc_links_to_html.lua

@@ -0,0 +1,11 @@
+-- Based on https://stackoverflow.com/a/49396058 (CC-BY-SA 4.0)
+
+local extensions_by_format = {
+	["html"] = ".html",
+	["asciidoc"] = ".adoc",
+}
+
+function Link(el)
+	el.target = string.gsub(el.target, "%.md", extensions_by_format[FORMAT])
+	return el
+end