Convert tool/extract-changes.hs to a Lua filter.

Makefile

@@ -75,7 +75,7 @@ fix_spacing: ## Fix trailing newlines and spaces
 	for f in $(SOURCEFILES); do printf '%s\n' "`cat $$f`" | sed -e 's/  *$$//' > $$f.tmp; mv $$f.tmp $$f; done
 
 changes_github: ## copy this release's changes in gfm
-	pandoc --filter tools/extract-changes.hs changelog.md -t gfm --wrap=none --template tools/changes_template.html | sed -e 's/\\#/#/g' | pbcopy
+	pandoc --lua-filter tools/extract-changes.lua changelog.md -t gfm --wrap=none --template tools/changes_template.html | sed -e 's/\\#/#/g' | pbcopy
 
 
 debpkg: ## create linux package

tools/extract-changes.hs

@@ -1,15 +0,0 @@
-#!/usr/bin/env stack
--- stack --stack-yaml=stack.yaml runghc --package pandoc-types
-
--- Extract changes from latest version in changelog.
-import Text.Pandoc.JSON
-
-main = toJSONFilter extractFirst
-
-extractFirst :: Pandoc -> Pandoc
-extractFirst (Pandoc meta bs) =
-  let bs' = dropWhile (not . isSubhead) bs
-   in Pandoc meta (takeWhile (not . isSubhead) (drop 1 bs'))
-
-isSubhead (Header 2 _ _) = True
-isSubhead _ = False

tools/extract-changes.lua

@@ -0,0 +1,18 @@
+-- Extract changes from latest version in changelog.
+
+function Pandoc(el)
+  local newblocks = {}
+  i = 1
+  while i <= #el.blocks and
+      not (el.blocks[i].t == "Header" and el.blocks[i].level == 2) do
+    i = i+1
+  end
+  while i <= #el.blocks do
+    i = i+1
+    if el.blocks[i].t == "Header" and el.blocks[i].level == 2 then
+      break
+    end
+    table.insert(newblocks, el.blocks[i])
+  end
+  return pandoc.Pandoc(newblocks)
+end