Refactor book:build task

Rakefile

@@ -11,49 +11,74 @@ namespace :book do
   if version_string.empty?
     version_string = '0'
   end
-  date_string = Time.now.strftime("%Y-%m-%d")
+  date_string = Time.now.strftime('%Y-%m-%d')
   params = "--attribute revnumber='#{version_string}' --attribute revdate='#{date_string}'"
+  header_hash = `git rev-parse --short HEAD`.strip
+
+  # Check contributors list
+  # This checks commit hash stored in the header of list against current HEAD
+  def check_contrib
+    if File.exist?('book/contributors.txt')
+      current_head_hash = `git rev-parse --short HEAD`.strip
+      header = `head -n 1 book/contributors.txt`.strip
+      # Match regex, then coerce resulting array to string by join
+      header_hash = header.scan(/[a-f0-9]{7,}/).join
+
+      if header_hash == current_head_hash
+        puts "Hash on header of contributors list (#{header_hash}) matches the current HEAD (#{current_head_hash})"
+      else
+        puts "Hash on header of contributors list (#{header_hash}) does not match the current HEAD (#{current_head_hash}), refreshing"
+        `rm book/contributors.txt`
+        # Reenable and invoke task again
+        Rake::Task['book/contributors.txt'].reenable
+        Rake::Task['book/contributors.txt'].invoke
+      end
+    end
+  end
 
   desc 'build basic book formats'
   task :build => [:build_html, :build_epub, :build_pdf] do
     begin
         # Run check
-        Rake::Task["book:check"].invoke
+        Rake::Task['book:check'].invoke
 
         # Rescue to ignore checking errors
         rescue => e
         puts e.message
-        puts "Error when checking books (ignored)"
+        puts 'Error when checking books (ignored)'
     end
   end
 
   desc 'build basic book formats (for ci)'
   task :ci => [:build_html, :build_epub, :build_pdf] do
-    begin
-        # Run check, but don't ignore any errors
-        Rake::Task["book:check"].invoke
-    end
+      # Run check, but don't ignore any errors
+      Rake::Task['book:check'].invoke
   end
 
   desc 'generate contributors list'
   file 'book/contributors.txt' do
-      puts "Generating contributors list"
-      `git shortlog -s | grep -v -E "(Straub|Chacon|dependabot)" | cut -f 2- | column -c 120 > book/contributors.txt`
+      puts 'Generating contributors list'
+      `echo "Contributors as of #{header_hash}:\n" > book/contributors.txt`
+      `git shortlog -s | grep -v -E "(Straub|Chacon|dependabot)" | cut -f 2- | column -c 120 >> book/contributors.txt`
   end
 
   desc 'build HTML format'
   task :build_html => 'book/contributors.txt' do
-      puts "Converting to HTML..."
+      check_contrib()
+
+      puts 'Converting to HTML...'
       `bundle exec asciidoctor #{params} -a data-uri progit.asc`
-      puts " -- HTML output at progit.html"
+      puts ' -- HTML output at progit.html'
 
   end
 
   desc 'build Epub format'
   task :build_epub => 'book/contributors.txt' do
-      puts "Converting to EPub..."
+      check_contrib()
+
+      puts 'Converting to EPub...'
       `bundle exec asciidoctor-epub3 #{params} progit.asc`
-      puts " -- Epub output at progit.epub"
+      puts ' -- Epub output at progit.epub'
 
   end
 
@@ -70,38 +95,41 @@ namespace :book do
       # FIXME: If asciidoctor-epub3 supports Mobi again, uncomment these lines below
       puts "Converting to Mobi isn't supported yet."
       puts "For more information see issue #1496 at https://github.com/progit/progit2/issues/1496."
+>>>>>>> fork/build-task-refactor
       exit(127)
   end
 
   desc 'build PDF format'
   task :build_pdf => 'book/contributors.txt' do
-      puts "Converting to PDF... (this one takes a while)"
+      check_contrib()
+
+      puts 'Converting to PDF... (this one takes a while)'
       `bundle exec asciidoctor-pdf #{params} progit.asc 2>/dev/null`
-      puts " -- PDF output at progit.pdf"
+      puts ' -- PDF output at progit.pdf'
   end
 
   desc 'Check generated books'
   task :check => [:build_html, :build_epub] do
-    begin
-        puts "Checking generated books"
+      puts 'Checking generated books'
 
-        exec_or_raise('htmlproofer --check-html progit.html')
-        exec_or_raise('epubcheck progit.epub')
-    end
+      exec_or_raise('htmlproofer --check-html progit.html')
+      exec_or_raise('epubcheck progit.epub')
   end
 
   desc 'Clean all generated files'
   task :clean do
     begin
-        puts "Removing generated files"
+        puts 'Removing generated files'
 
         FileList['book/contributors.txt', 'progit.html', 'progit.epub', 'progit.pdf'].each do |file|
             rm file
 
             # Rescue if file not found
             rescue Errno::ENOENT => e
-            puts e.message
-            puts "Error removing files (ignored)"
+              begin
+                  puts e.message
+                  puts 'Error removing files (ignored)'
+              end
         end
     end
   end