An example Fastfile

Fastfile

# This is the minimum version number required.
# Update this, if you use features of a newer version
fastlane_version "1.41.0"

default_platform :ios

platform :ios do
  before_all do
    ENV["SLACK_URL"] = "https://hooks.slack.com/services/MoneyWithWings"

    # Make sure there are no uncommitted changeds
    ensure_git_status_clean

    # Update cocoapods
    cocoapods
  end

  desc "Build and sign the app"
  private_lane :build_app do |options|
    increment_build_number

    # Build the app
    gym(
      workspace: "MoneyWithWings.xcworkspace",
      scheme: "MoneyWithWings Beta",
      configuration: "Release"
    )
  end

  desc "Submit a new Beta Build to Apple TestFlight"
  desc "This action will also do a build version bump and push it to git."
  lane :beta do
    build_app
    
    pilot(
      skip_submission: true
    )

    # Make sure our directory is clean, except for changes Fastlane has made
    clean_build_artifacts

    version_number = get_version_number
    build_number = get_build_number
    tag = "beta/#{version_number}/#{build_number}"

    commit_version_bump(
      message: "Version Bump to #{version_number}-#{build_number}"
    )
    
    add_git_tag(tag: tag)

    push_to_git_remote
  end

  # On success, post in Slack!
  after_all do |lane|
    slack(
      message: "💸💸💸 Successfully deployed new iOS App Update 💸💸💸"
    )
  end

  # On failure, let us know what went wrong in Slack, and then revert the git repo to the previous state.
  error do |lane, exception|
    slack(
      message: exception.message,
      success: false
    )

    reset_git_repo
  end
end

If you're incrementing the build number and tagging it after build_app and pilot, doesn't that mean the uploaded build will always be one number behind what is tagged?

EDIT: Nevermind, I just noticed that the incrementing is done before the build, and only the commit and tag are done after it. Nice job :)