Rake task to create git tag with timestamp and all the merge events since last tag

git.rake

namespace :git do
  desc 'Create a tag with release name and merge events since last tag'

  # expects merge events with no-ff, as gitlab does by default

  APP_NAME = ''
  MERGE_EVENTS_SINCE_LAST_TAG =
    `git log \`git describe --tags --abbrev=0\`..HEAD --merges --oneline`

  def release_name
    "#{APP_NAME}_release-#{Time.now.utc.strftime("%Y%m%d%H%M%S")}"
  end

  task :create_release do
    release_name = "#{release_name}"
    puts "Tagging release as '#{release_name}'"
    sh "git tag -a #{release_name} -m \"#{MERGE_EVENTS_SINCE_LAST_TAG}\""
    sh "git push origin --tags"
  end
end