1 files changed, 41 insertions, 0 deletions
diff --git a/tool/update-NEWS-gemlist.rb b/tool/update-NEWS-gemlist.rb
new file mode 100755
index 0000000000..8e4d39046b
--- /dev/null
+++ b/tool/update-NEWS-gemlist.rb
@@ -0,0 +1,41 @@
+#!/usr/bin/env ruby
+require 'json'
+news = File.read("NEWS.md")
+prev = news[/since the \*+(\d+\.\d+\.\d+)\*+/, 1]
+prevs = [prev, prev.sub(/\.\d+\z/, '')]
+
+update = ->(list, type, desc = "updated") do
+  item = ->(mark = "* ") do
+    "The following #{type} gem#{list.size == 1 ? ' is' : 's are'} #{desc}.\n\n" +
+      list.map {|g, v|"#{mark}#{g} #{v}\n"}.join("") + "\n"
+  end
+  news.sub!(/^(?:\*( +))?The following #{type} gems? (?:are|is) #{desc}\.\n+(?:(?(1) \1)\*( *).*\n)*\n*/) do
+    item["#{$1&.<< " "}*#{$2 || ' '}"]
+  end or news.sub!(/^## Stdlib updates(?:\n+The following.*(?:\n+( *\* *).*)*)*\n+\K/) do
+    item[$1 || "* "]
+  end
+end
+ARGV.each do |type|
+  last = JSON.parse(File.read("#{type}_gems.json"))['gems'].filter_map do |g|
+    v = g['versions'].values_at(*prevs).compact.first
+    g = g['gem']
+    g = 'RubyGems' if g == 'rubygems'
+    [g, v] if v
+  end.to_h
+  changed = File.foreach("gems/#{type}_gems").filter_map do |l|
+    next if l.start_with?("#")
+    g, v = l.split(" ", 3)
+    next unless v
+    [g, v] unless last[g] == v
+  end
+  changed, added = changed.partition {|g, _| last[g]}
+  update[changed, type] or next
+  if added and !added.empty?
+    if type == 'bundled'
+      update[added, type, 'promoted from default gems'] or next
+    else
+      update[added, type, 'added'] or next
+    end
+  end
+  File.write("NEWS.md", news)
+end