Lookup migration by file name, then get the version number (rails). Handy for migrating up + down based on the migration name (for instance `rake db:migrate VERSION=$(migration_before create_users)`)

migration_before.rb

#!/usr/bin/env ruby

name = ARGV[0]
verbose = ARGV[1] == "--verbose"

if name.nil? || name.empty?
  puts ""
  puts "\tUsage: migration_before <migration_name> [--verbose]"
  puts ""
  puts "\tLookup migration by file name, then get the version number (rails).  "
  puts "\tHandy for migrating up + down based on the migration name (for instance "
  puts "\t`rake db:migrate VERSION=$(migration_before create_users)`)"
  puts ""
  puts "\tExample Output:"
  puts "\t\t$ migration_before create_users"
  puts "\t\t20200113191953"

  exit -1
end

files = Dir.glob("db/migrate/*.rb").sort.reverse
matching_index = nil

reversed_files = files.reverse

reversed_files.each_with_index do |file, index|
  file =~ /(\d+)_(.*)\.rb/
  migration_name = $2

  if verbose
    puts "file: #{file}"
  end

  if migration_name.include?(name)
    if verbose
      puts "matching migration: #{migration_name} (#{file})"
    end
    matching_index = index
  end
end

if !matching_index
  raise "* no matching index with name: #{name}"
end

file_before = reversed_files[matching_index - 1]
version_before = (file_before =~ /(\d+)_(.*)\.rb/) && $1

if verbose
  puts "* Found Matching File: #{reversed_files[matching_index]}"
  puts "* Migrating to: #{file_before} (#{version_before})"
end

puts version_before