🔨 Update checksums script

- rubygems/guides#325

bin/checksums

@@ -1,9 +1,14 @@
 #!/usr/bin/env ruby
 # frozen_string_literal: true
 
+# Script from https://github.com/rubygems/guides/pull/325
 require "digest/sha2"
 
-VERSION_REGEX = /\d+\.\d+\.\d+([-.].+)*/.freeze
+# Final clause of Regex `(?=\.gem)` is a positive lookahead assertion
+# See: https://learnbyexample.github.io/Ruby_Regexp/lookarounds.html#positive-lookarounds
+# Used to pattern match against a gem package name, which always ends with .gem.
+# The positive lookahead ensures it is present, and prevents it from being captured.
+VERSION_REGEX = /((\d+\.\d+\.\d+)([-.][0-9A-Za-z-]+)*)(?=\.gem)/.freeze
 
 gem_path_parts = ARGV.first&.split("/")
 
@@ -36,7 +41,7 @@ checksum256 = Digest::SHA256.new.hexdigest(File.read(gem_pkg))
 checksum256_path = "checksums/#{gem_name}.sha256"
 File.write(checksum256_path, checksum256)
 
-version = File.basename(checksum256_path[VERSION_REGEX], ".gem")
+version = gem_name[VERSION_REGEX]
 
 git_cmd = <<~GIT_MSG
 git add checksums/* && \
@@ -48,7 +53,9 @@ puts <<~RESULTS
 [VERSION: #{version}]
 [CHECKSUM SHA256 PATH: #{checksum256_path}]
 [CHECKSUM SHA512 PATH: #{checksum512_path}]
+
 ... Running ...
+
 #{git_cmd}
 RESULTS