use faster worktree instead of cloning

extracted from #944

app/models/git_repository.rb

@@ -24,9 +24,8 @@ def checkout_workspace(work_dir, git_reference)
     executor.output.write("# Beginning git repo setup\n")
 
     ensure_mirror_current &&
-    create_workspace(work_dir) &&
-    checkout(git_reference, work_dir) &&
-    checkout_submodules(work_dir)
+      checkout(git_reference, work_dir) &&
+      checkout_submodules(work_dir)
   end
 
   # @return [nil, sha1]
@@ -91,6 +90,11 @@ def update_mirror
     exclusive { (mirrored? ? update! : clone!) }
   end
 
+  # clear worktrees that are deleted
+  def prune_worktree
+    executor.execute("cd #{repo_cache_dir}", "git worktree prune")
+  end
+
   private
 
   attr_reader :repository_url, :repository_directory
@@ -129,11 +133,6 @@ def clone!
   end
   add_tracer :clone!
 
-  def create_workspace(temp_dir)
-    executor.execute "git clone #{repo_cache_dir} #{temp_dir}"
-  end
-  add_tracer :create_workspace
-
   def update!
     executor.execute("cd #{repo_cache_dir}", 'git fetch -p')
   end
@@ -143,25 +142,23 @@ def sha_exist?(sha)
     !!capture_stdout("git", "cat-file", "-t", sha)
   end
 
-  def checkout(git_reference, pwd)
-    executor.execute("cd #{pwd}", "git checkout --quiet #{git_reference.shellescape}")
+  def checkout(git_reference, work_dir)
+    executor.execute(
+      "cd #{repo_cache_dir}",
+      "git worktree add #{work_dir.shellescape} #{git_reference.shellescape} --force"
+    )
   end
 
   def checkout_submodules(pwd)
     return true unless File.exist? "#{pwd}/.gitmodules"
 
-    recursive_flag = " --recursive" if git_supports_recursive_flag?
     executor.execute(
       "cd #{pwd}",
-      "git submodule sync#{recursive_flag}",
+      "git submodule sync --recursive",
       "git submodule update --init --recursive"
     )
   end
 
-  def git_supports_recursive_flag?
-    Samson::GitInfo.version >= Gem::Version.new("1.8.1")
-  end
-
   def mirrored?
     Dir.exist?(repo_cache_dir)
   end

app/models/job_execution.rb

@@ -271,6 +271,7 @@ def build_finder
     @build_finder ||= Samson::BuildFinder.new(@output, @job, @reference)
   end
 
+  # TODO: @repository.checkout_workspace should manage the tempdir and prune after
   def make_tempdir
     result = nil
     Dir.mktmpdir("samson-#{@job.project.permalink}-#{@job.id}") do |dir|
@@ -279,5 +280,7 @@ def make_tempdir
   rescue Errno::ENOTEMPTY, Errno::ENOENT
     ErrorNotifier.notify("Notify: make_tempdir error #{$!.message.split('@').first}")
     result # tempdir ensure sometimes fails ... not sure why ... return normally
+  ensure
+    @repository.prune_worktree
   end
 end

config/initializers/git.rb

@@ -0,0 +1,4 @@
+# frozen_string_literal: true
+min = "2.5.0"
+raise "Git not found" unless version = `git --version`[/\d+\.\d+\.\d+/]
+raise "Need git v#{min}+" if Gem::Version.new(version) < Gem::Version.new(min)

test/models/git_repository_test.rb

@@ -22,25 +22,6 @@
     repository.send(:repository_directory).must_equal project.repository_directory
   end
 
-  describe "#create_workspace" do
-    it 'clones a repository' do
-      Dir.mktmpdir do |dir|
-        create_repo_without_tags
-        FileUtils.mv(repo_temp_dir, repository.repo_cache_dir)
-
-        repository.send(:create_workspace, dir).must_equal true
-        Dir.exist?("#{dir}/.git").must_equal true
-      end
-    end
-
-    it "returns false when clone fails" do
-      Dir.mktmpdir do |dir|
-        repository.send(:create_workspace, dir).must_equal false
-        Dir.exist?("#{dir}/.git").must_equal false
-      end
-    end
-  end
-
   describe "#ensure_mirror_current" do
     def call
       repository.send(:ensure_mirror_current)
@@ -95,24 +76,14 @@ def call
       public = file.split(/^  private$/).first
       methods = public.scan(/^  def ([a-z_\?\!]+)(.*?)^  end/m)
       methods.size.must_be :>, 5 # making sure the logic is sound
-      methods.delete_if { |method, _| method == "update_mirror" }
+      methods.delete_if { |method, _| ["update_mirror", "prune_worktree"].include?(method) }
       methods.each do |name, body|
         next if ["initialize", "repo_cache_dir", "clean!", "valid_url?"].include?(name)
         body.must_include "ensure_mirror_current", "Expected #{name} to update the repo with ensure_mirror_current"
       end
     end
   end
 
-  describe "#checkout" do
-    it 'switches to a different branch' do
-      create_repo_with_an_additional_branch
-      repository.send(:checkout, 'master', repo_temp_dir).must_equal(true)
-      Dir.chdir(repo_temp_dir) { current_branch.must_equal('master') }
-      repository.send(:checkout, 'test_user/test_branch', repo_temp_dir).must_equal(true)
-      Dir.chdir(repo_temp_dir) { current_branch.must_equal('test_user/test_branch') }
-    end
-  end
-
   describe "#commit_from_ref" do
     it 'returns the full commit id' do
       create_repo_with_tags

test/models/job_execution_test.rb

@@ -38,6 +38,7 @@ def last_line_of_output
     user.name = 'John Doe'
     user.email = '[email protected]'
     project.repository.send(:clone!)
+    project.repository.stubs(:prune_worktree)
     job.deploy = deploy
     freeze_time
   end
@@ -478,5 +479,14 @@ def perform
         111
       end.must_equal 111
     end
+
+    it "removes deleted worktrees" do
+      project.repository.unstub(:prune_worktree)
+      before = `cd #{project.repository.repo_cache_dir} && git worktree list`
+      execution.send(:make_tempdir) do |dir|
+        assert project.repository.checkout_workspace(dir, "master")
+      end
+      `cd #{project.repository.repo_cache_dir} && git worktree list`.must_equal before
+    end
   end
 end