Change the approach to check if patches apply cleanly

.gitlab-ci.yml

@@ -210,7 +210,7 @@ rake brakeman: *exec
 rake flay: *exec
 license_finder: *exec
 rake downtime_check: *exec
-rake ce_to_ee_merge_check:
+rake ee_compat_check:
   <<: *exec
   only:
     - branches

lib/gitlab/ee_compat_check.rb

+module Gitlab
+  # Checks if a set of migrations requires downtime or not.
+  class EeCompatCheck
+    EE_REPO = 'https://gitlab.com/gitlab-org/gitlab-ee.git'.freeze
+
+    attr_reader :ce_branch, :check_dir, :ce_repo
+
+    def initialize(branch:, check_dir:, ce_repo: nil)
+      @ce_branch = branch
+      @check_dir = check_dir
+      @ce_repo = ce_repo || 'https://gitlab.com/gitlab-org/gitlab-ce.git'
+    end
+
+    def check
+      ensure_ee_repo
+      delete_patches
+
+      generate_patch(ce_branch, ce_patch_full_path)
+
+      Dir.chdir(check_dir) do
+        step("In the #{check_dir} directory")
+
+        step("Pulling latest master", %w[git pull --ff-only origin master])
+
+        status = catch(:halt_check) do
+          ce_branch_compat_check!
+
+          delete_ee_branch_locally
+
+          ee_branch_presence_check!
+
+          ee_branch_compat_check!
+        end
+
+        delete_ee_branch_locally
+        delete_patches
+
+        if status.nil?
+          true
+        else
+          false
+        end
+      end
+    end
+
+    private
+
+    def ensure_ee_repo
+      if Dir.exist?(check_dir)
+        step("#{check_dir} already exists")
+      else
+        cmd = %W[git clone --branch master --single-branch --depth 1 #{EE_REPO} #{check_dir}]
+        step("Cloning #{EE_REPO} into #{check_dir}", cmd)
+      end
+    end
+
+    def ce_branch_compat_check!
+      cmd = %W[git apply --check #{ce_patch_full_path}]
+      status = step("Checking if #{ce_patch_name} applies cleanly to EE/master", cmd)
+
+      if status.zero?
+        puts ce_applies_cleanly_msg(ce_branch)
+        throw(:halt_check)
+      end
+    end
+
+    def ee_branch_presence_check!
+      status = step("Fetching origin/#{ee_branch}", %W[git fetch origin #{ee_branch}])
+
+      unless status.zero?
+        puts
+        puts ce_branch_doesnt_apply_cleanly_and_no_ee_branch_msg
+
+        throw(:halt_check, :ko)
+      end
+    end
+
+    def ee_branch_compat_check!
+      step("Checking out origin/#{ee_branch}", %W[git checkout -b #{ee_branch} FETCH_HEAD])
+
+      generate_patch(ee_branch, ee_patch_full_path)
+      cmd = %W[git apply --check #{ee_patch_full_path}]
+      status = step("Checking if #{ee_patch_name} applies cleanly to EE/master", cmd)
+
+      unless status.zero?
+        puts
+        puts ee_branch_doesnt_apply_cleanly_msg
+
+        throw(:halt_check, :ko)
+      end
+
+      puts
+      puts ee_applies_cleanly_msg
+    end
+
+    def generate_patch(branch, filepath)
+      FileUtils.rm(filepath, force: true)
+
+      depth = 0
+      loop do
+        depth += 10
+        step("Fetching origin/master", %W[git fetch origin master --depth=#{depth}])
+        status = step("Finding merge base with master", %W[git merge-base FETCH_HEAD #{branch}])
+
+        break if status.zero? || depth > 500
+      end
+
+      raise "#{branch} is too far behind master, please rebase it!" if depth > 500
+
+      step("Generating the patch against master")
+      output, status = Gitlab::Popen.popen(%w[git format-patch FETCH_HEAD --stdout])
+      throw(:halt_check, :ko) unless status.zero?
+
+      File.open(filepath, 'w+') { |f| f.write(output) }
+      throw(:halt_check, :ko) unless File.exist?(filepath)
+    end
+
+    def delete_ee_branch_locally
+      step("Checking out origin/master", %w[git checkout master])
+      step("Deleting the local #{ee_branch} branch", %W[git branch -D #{ee_branch}])
+    end
+
+    def delete_patches
+      step("Deleting #{ce_patch_full_path}")
+      FileUtils.rm(ce_patch_full_path, force: true)
+
+      step("Deleting #{ee_patch_full_path}")
+      FileUtils.rm(ee_patch_full_path, force: true)
+    end
+
+    def ce_patch_name
+      @ce_patch_name ||= "#{ce_branch}.patch"
+    end
+
+    def ce_patch_full_path
+      @ce_patch_full_path ||= File.expand_path(ce_patch_name, check_dir)
+    end
+
+    def ee_branch
+      @ee_branch ||= "#{ce_branch}-ee"
+    end
+
+    def ee_patch_name
+      @ee_patch_name ||= "#{ee_branch}.patch"
+    end
+
+    def ee_patch_full_path
+      @ee_patch_full_path ||= File.expand_path(ee_patch_name, check_dir)
+    end
+
+    def step(desc, cmd = nil)
+      puts "\n=> #{desc}\n"
+
+      if cmd
+        puts "\n$ #{cmd.join(' ')}"
+        command(cmd)
+      end
+    end
+
+    def command(cmd)
+      output, status = Gitlab::Popen.popen(cmd)
+      puts output
+
+      status
+    end
+
+    def ce_applies_cleanly_msg(ce_branch)
+      <<-MSG.strip_heredoc
+        =================================================================
+        🎉 Congratulations!! 🎉
+
+        The #{ce_branch} branch applies cleanly to EE/master!
+
+        Much ❤️!!
+        =================================================================\n
+      MSG
+    end
+
+    def ce_branch_doesnt_apply_cleanly_and_no_ee_branch_msg
+      <<-MSG.strip_heredoc
+        =================================================================
+        💥 Oh no! 💥
+
+        The #{ce_branch} branch does not apply cleanly to the current
+        EE/master, and no #{ee_branch} branch was found in the EE repository.
+
+        Please create a #{ee_branch} branch that includes changes from
+        #{ce_branch} but also specific changes than can be applied cleanly
+        to EE/master.
+
+        There are different ways to create such branch:
+
+        1. Create a new branch based on the CE branch and rebase it on top of EE/master
+
+          # In the EE repo
+          $ git fetch #{ce_repo} #{ce_branch}
+          $ git checkout -b #{ee_branch} FETCH_HEAD
+
+          # You can squash the #{ce_branch} commits into a single "Port of #{ce_branch} to EE" commit
+          # before rebasing to limit the conflicts-resolving steps during the rebase
+          $ git fetch origin
+          $ git rebase origin/master
+
+          At this point you will likely have conflicts.
+          Solve them, and continue/finish the rebase.
+
+          You can squash the #{ce_branch} commits into a single "Port of #{ce_branch} to EE".
+
+        2. Create a new branch from master and cherry-pick your CE commits
+
+          # In the EE repo
+          $ git fetch origin
+          $ git checkout -b #{ee_branch} FETCH_HEAD
+          $ git fetch #{ce_repo} #{ce_branch}
+          $ git cherry-pick SHA # Repeat for all the commits you want to pick
+
+          You can squash the #{ce_branch} commits into a single "Port of #{ce_branch} to EE" commit.
+
+        Don't forget to push your branch to #{EE_REPO}:
+
+          # In the EE repo
+          $ git push origin #{ee_branch}
+
+        You can then retry this failed build, and hopefully it should pass.
+
+        Stay 💪 !
+        =================================================================\n
+      MSG
+    end
+
+    def ee_branch_doesnt_apply_cleanly_msg
+      <<-MSG.strip_heredoc
+        =================================================================
+        💥 Oh no! 💥
+
+        The #{ce_branch} does not apply cleanly to the current
+        EE/master, and even though a #{ee_branch} branch exists in the EE
+        repository, it does not apply cleanly either to EE/master!
+
+        Please update the #{ee_branch}, push it again to #{EE_REPO}, and
+        retry this build.
+
+        Stay 💪 !
+        =================================================================\n
+      MSG
+    end
+
+    def ee_applies_cleanly_msg
+      <<-MSG.strip_heredoc
+        =================================================================
+        🎉 Congratulations!! 🎉
+
+        The #{ee_branch} branch applies cleanly to EE/master!
+
+        Much ❤️!!
+        =================================================================\n
+      MSG
+    end
+  end
+end

lib/tasks/ce_to_ee_merge_check.rake → lib/tasks/ee_compat_check.rake

 desc 'Checks if the branch would apply cleanly to EE'
-task ce_to_ee_merge_check: :environment do
-  Rake::Task['gitlab:dev:ce_to_ee_merge_check'].invoke
+task ee_compat_check: :environment do
+  Rake::Task['gitlab:dev:ee_compat_check'].invoke
 end

lib/tasks/gitlab/dev.rake

 namespace :gitlab do
   namespace :dev do
     desc 'Checks if the branch would apply cleanly to EE'
-    task ce_to_ee_merge_check: :environment do
+    task ee_compat_check: :environment do
       return if defined?(Gitlab::License)
       return unless ENV['CI']
 
-      ce_repo = ENV['CI_BUILD_REPO']
-      ce_branch = ENV['CI_BUILD_REF_NAME']
-
-      ee_repo = 'https://gitlab.com/gitlab-org/gitlab-ee.git'
-      ee_branch = "#{ce_branch}-ee"
-      ee_dir = 'gitlab-ee-merge-check'
-
-      puts "\n=> Cloning #{ee_repo} into #{ee_dir}\n"
-      `git clone #{ee_repo} #{ee_dir} --depth 1`
-      Dir.chdir(ee_dir) do
-        puts "\n => Fetching #{ce_repo}/#{ce_branch}\n"
-        `git fetch #{ce_repo} #{ce_branch} --depth 1`
-
-        # Try to merge the current tested branch to EE/master...
-        puts "\n => Merging #{ce_repo}/#{ce_branch} into #{ee_repo}/master\n"
-        `git merge FETCH_HEAD`
-
-        exit 0 if $?.success?
-
-        # Check if the <branch>-ee branch exists...
-        puts "\n => Check if #{ee_repo}/#{ee_branch} exists\n"
-        `git rev-parse --verify #{ee_branch}`
-
-        # The <branch>-ee doesn't exist
-        unless $?.success?
-          puts
-          puts <<-MSG.strip_heredoc
-            =================================================================
-            The #{ce_branch} branch cannot be merged without conflicts to the
-            current EE/master, and no #{ee_branch} branch was detected in
-            the EE repository.
-
-            Please create a #{ee_branch} branch that includes changes from
-            #{ce_branch} but also specific changes than can be applied cleanly
-            to EE/master.
-
-            You can create this branch as follows:
-
-            1. In the EE repo:
-              $ git fetch origin
-              $ git fetch #{ce_repo} #{ce_branch}
-              $ git checkout -b #{ee_branch} FETCH_HEAD
-              $ git rebase origin/master
-            2. At this point you will likely have conflicts, solve them, and
-              continue/finish the rebase. Note: You can squash the CE commits
-              before rebasing.
-            3. You can squash all the original #{ce_branch} commits into a
-              single "Port of #{ce_branch} to EE".
-            4. Push your branch to #{ee_repo}:
-              $ git push origin #{ee_branch}
-            =================================================================\n
-          MSG
+      success =
+        Gitlab::EeCompatCheck.new(
+          branch: ENV['CI_BUILD_REF_NAME'],
+          check_dir: File.expand_path('ee-compat-check', __dir__),
+          ce_repo: ENV['CI_BUILD_REPO']
+        ).check
 
+      if success
+        exit 0
+      else
         exit 1
       end
-
-        # Try to merge the <branch>-ee branch to EE/master...
-        puts "\n => Merging #{ee_repo}/#{ee_branch} into #{ee_repo}/master\n"
-        `git merge #{ee_branch} master`
-
-        # The <branch>-ee cannot be merged cleanly to EE/master...
-        unless $?.success?
-          puts
-          puts <<-MSG.strip_heredoc
-            =================================================================
-            The #{ce_branch} branch cannot be merged without conflicts to
-            EE/master, and even though the #{ee_branch} branch exists in the EE
-            repository, it cannot be merged without conflicts to EE/master.
-
-            Please update the #{ee_branch}, push it again to #{ee_repo}, and
-            retry this job.
-            =================================================================\n
-          MSG
-
-          exit 2
-        end
-
-        puts "\n => Merging #{ce_repo}/#{ce_branch} into #{ee_repo}/master\n"
-        `git merge FETCH_HEAD`
-        exit 0 if $?.success?
-
-        # The <branch>-ee can be merged cleanly to EE/master, but <branch> still
-        # cannot be merged cleanly to EE/master...
-        puts
-        puts <<-MSG.strip_heredoc
-          =================================================================
-          The #{ce_branch} branch cannot be merged without conflicts to EE, and
-          even though the #{ee_branch} branch exists in the EE repository and
-          applies cleanly to EE/master, it doesn't prevent conflicts when
-          merging #{ce_branch} into EE.
-
-          We may be in a complex situation here.
-          =================================================================\n
-        MSG
-
-        exit 3
-      end
     end
   end
 end