herokuにデプロイ出来ない

Question

前提・実現したいこと

herokuにデプロイしようとしたところエラーが発生しました。

発生している問題・エラーメッセージ

ターミナル

➜  taskleaf git:(master) ✗ git push heroku master
Enumerating objects: 185, done.
Counting objects: 100% (185/185), done.
Delta compression using up to 8 threads
Compressing objects: 100% (162/162), done.
Writing objects: 100% (185/185), 46.41 KiB | 3.87 MiB/s, done.
Total 185 (delta 28), reused 0 (delta 0), pack-reused 0
remote: Compressing source files... done.
remote: Building source:
remote: 
remote: -----> Building on the Heroku-20 stack
remote: -----> Determining which buildpack to use for this app
remote:  !     Warning: Multiple default buildpacks reported the ability to handle this app. The first buildpack in the list below will be used.
remote: 			Detected buildpacks: Ruby,Node.js
remote: 			See https://devcenter.heroku.com/articles/buildpacks#buildpack-detect-order
remote: -----> Ruby app detected
remote: -----> Installing bundler 2.2.16
remote: -----> Removing BUNDLED WITH version in the Gemfile.lock
remote: -----> Compiling Ruby/Rails
remote:        Command: 'set -o pipefail; curl -L --fail --retry 5 --retry-delay 1 --connect-timeout 3 --max-time 30 https://s3-external-1.amazonaws.com/heroku-buildpack-ruby/heroku-20/ruby-2.5.1.tgz -s -o - | tar zxf - ' failed on attempt 1 of 3.
remote:        Command: 'set -o pipefail; curl -L --fail --retry 5 --retry-delay 1 --connect-timeout 3 --max-time 30 https://s3-external-1.amazonaws.com/heroku-buildpack-ruby/heroku-20/ruby-2.5.1.tgz -s -o - | tar zxf - ' failed on attempt 2 of 3.
remote: 
remote:  !
remote:  !     The Ruby version you are trying to install does not exist on this stack.
remote:  !     
remote:  !     You are trying to install ruby-2.5.1 on heroku-20.
remote:  !     
remote:  !     Ruby ruby-2.5.1 is present on the following stacks:
remote:  !     
remote:  !     - cedar-14
remote:  !     - heroku-16
remote:  !     - heroku-18
remote:  !     
remote:  !     Heroku recommends you use the latest supported Ruby version listed here:
remote:  !     https://devcenter.heroku.com/articles/ruby-support#supported-runtimes
remote:  !     
remote:  !     For more information on syntax for declaring a Ruby version see:
remote:  !     https://devcenter.heroku.com/articles/ruby-versions
remote:  !
remote:  !     Push rejected, failed to compile Ruby app.
remote: 
remote:  !     Push failed
remote:  !
remote:  ! ## Warning - The same version of this code has already been built: c42d7369dc43505eff8f452ebc36e30d8ede3e26
remote:  !
remote:  ! We have detected that you have triggered a build from source code with version c42d7369dc43505eff8f452ebc36e30d8ede3e26
remote:  ! at least twice. One common cause of this behavior is attempting to deploy code from a different branch.
remote:  !
remote:  ! If you are developing on a branch and deploying via git you must run:
remote:  !
remote:  !     git push heroku <branchname>:main
remote:  !
remote:  ! This article goes into details on the behavior:
remote:  !   https://devcenter.heroku.com/articles/duplicate-build-version
remote: 
remote: Verifying deploy...
remote: 
remote: !	Push rejected to rails-taskapp.
remote: 
To https://git.heroku.com/rails-taskapp.git
 ! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to 'https://git.heroku.com/rails-taskapp.git'
➜  taskleaf git:(master) ✗ 

該当のソースコード

Gemfile

source 'https://rubygems.org'
git_source(:github) { |repo| "https://github.com/#{repo}.git" }

ruby '2.5.1'

# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '~> 5.2.4', '>= 5.2.4.5'
# Use postgresql as the database for Active Record
gem 'pg', '>= 0.18', '< 2.0'
# Use Puma as the app server
gem 'puma', '~> 3.11'
# Use SCSS for stylesheets
gem 'sass-rails', '~> 5.0'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
# See https://github.com/rails/execjs#readme for more supported runtimes
# gem 'mini_racer', platforms: :ruby

# Use CoffeeScript for .coffee assets and views
gem 'coffee-rails', '~> 4.2'
# Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
gem 'turbolinks', '~> 5'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 2.5'
# Use Redis adapter to run Action Cable in production
# gem 'redis', '~> 4.0'
 #Use ActiveModel has_secure_password
 gem 'bcrypt', '~> 3.1.7'

# Use ActiveStorage variant
# gem 'mini_magick', '~> 4.8'

# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development

# Reduces boot times through caching; required in config/boot.rb
gem 'bootsnap', '>= 1.1.0', require: false

group :development, :test do
  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
  gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
  gem 'rspec-rails', '~> 3.7'
  gem 'factory_bot_rails', '~> 4.11'
end

group :development do
  # Access an interactive console on exception pages or by calling 'console' anywhere in the code.
  gem 'web-console', '>= 3.3.0'
  gem 'listen', '>= 3.0.5', '< 3.2'
  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
  gem 'spring'
  gem 'spring-watcher-listen', '~> 2.0.0'
end

group :test do
  # Adds support for Capybara system testing and selenium driver
  gem 'capybara', '>= 2.15'
  gem 'selenium-webdriver'
  # Easy installation and use of chromedriver to run system tests with Chrome
  gem 'chromedriver-helper'
end

group :production do
end
# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

gem 'slim-rails'
gem 'html2slim'

gem 'bootstrap'
gem 'rails_autolink'
gem 'ransack'
gem 'kaminari'
gem 'jquery-rails'

試したこと

bundleのバージョンが違ったのかと思い、一度bundler再インストールし直してみましたが、解決することができませんでした。

補足情報（FW/ツールのバージョンなど）

ruby 2.5.1p57
rbenv 1.1.2
Bundler version 2.2.14
Rails 5.2.6

Answer 1

remote:  !     
remote:  !     Ruby ruby-2.5.1 is present on the following stacks:
remote:  !     
remote:  !     - cedar-14
remote:  !     - heroku-16
remote:  !     - heroku-18

このあたりのエラー分を見ると、ご利用されているherokuはHeroku-20 stackですが、Ruby2.5.1はHeroku-20には無いようです。そのためにエラーが起きていると思われます。
Rubyのバージョンを2.7系にあげたり、Heroku-18を利用されるといいと思いました

Heroku-20でサポートされているRubyのバージョンはこちらからご確認いただくのが正確です

https://devcenter.heroku.com/articles/ruby-support#ruby-versions