Adding Huborg::Client#synchronize_mailmap!

The method will take a given template (which confirms to [Git's
.mailmap file format](https://www.git-scm.com/docs/git-check-mailmap),
then iterates on all of the repositories, adding any non-duplicates,
then writing back to the template before creating pull requests against
each of the organization's non-archived repositories.

Rakefile

@@ -32,4 +32,13 @@ namespace :test do
     )
     client.audit_license
   end
+
+  task :mailmap do
+    require 'huborg'
+    client = Huborg::Client.new(
+      github_access_token: ENV.fetch("GITHUB_ACCESS_TOKEN"),
+      org_names: ENV.fetch("GITHUB_ORG_NAME")
+    )
+    client.synchronize_mailmap!(template: ENV.fetch("MAILMAP_TEMPLATE_FILENAME"))
+  end
 end

lib/huborg.rb

@@ -147,7 +147,7 @@ def audit_license(skip_private: true, skip_archived: true, allowed_licenses: :al
     def synchronize_mailmap!(template:, consolidated_template: template)
       mailmap_lines = Set.new
       File.read(template).split("\n").each do |line|
-        mailmap_lines << line unless line.blank?
+        mailmap_lines << line unless line.empty?
       end
 
       each_github_repository do |repo|