is_merge_commit_latest.rb

module Fastlane
  module Actions
    class IsMergeCommitLatestAction < Action
      def self.run(params)
        last_commit_hash = Action.sh("git log -1 --pretty=format:\"%H\"")
        last_merge_commit_hash = Action.sh("git log -1 --merges --pretty=format:\"%H\"")

        UI.message "Determine if the latest commit is merge commit."
        return false if last_commit_hash != last_merge_commit_hash
        
        branch_regex = params[:head_branch_name_regex]

        if branch_regex.nil? then
          return true
        else
          UI.message "Determine if the latest merge commit from expected head branch."
          UI.message "Regular expression of expected head branch: /#{branch_regex}/"
          last_commit_msg = Actions.last_git_commit_message()
          return /^Merge.*#{branch_regex}/ === last_commit_msg
        end
      end

      #####################################################
      # @!group Documentation
      #####################################################

      def self.description
        "Returns a boolean value indicating whether the latest commit is merge commit"
      end

      def self.details
        "If option 'head_branch_name_regex' is defined, returns true only when tha latest commit is merge commit from branch matches pattern defined in `head_branch_name_regex`"
      end

      def self.available_options
        [
          FastlaneCore::ConfigItem.new(key: :head_branch_name_regex,
                                       description: "Regular expression of head branch name. **IMPORTANT** Don't use '^' or '$'",
                                       optional: true)
        ]
      end

      def self.return_value
        "A boolean value indicating whether latest commit is merge commit"
      end

      def self.is_supported?(platform)
        true # All platform
      end
    end
  end
end