Fetch the merged branches at once

Fetch the merged branches at once, instead of checking it one
by one in the view. We don't cache this yet because this would
already much improve the performance.

EE for https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/14729

app/controllers/projects/branches_controller.rb

@@ -15,6 +15,8 @@ class Projects::BranchesController < Projects::ApplicationController
     respond_to do |format|
       format.html do
         @refs_pipelines = @project.pipelines.latest_successful_for_refs(@branches.map(&:name))
+        @merged_branch_names =
+          repository.merged_branch_names(@branches.map(&:name))
         # n+1: https://gitlab.com/gitlab-org/gitlab-ce/issues/37429
         Gitlab::GitalyClient.allow_n_plus_1_calls do
           @max_commits = @branches.reduce(0) do |memo, branch|

app/models/repository.rb

@@ -919,13 +919,20 @@ class Repository
     end
   end
 
-  def merged_to_root_ref?(branch_name)
-    branch_commit = commit(branch_name)
-    root_ref_commit = commit(root_ref)
+  def merged_to_root_ref?(branch_or_name, pre_loaded_merged_branches = nil)
+    branch = Gitlab::Git::Branch.find(self, branch_or_name)
+
+    if branch
+      root_ref_sha = commit(root_ref).sha
+      same_head = branch.target == root_ref_sha
+      merged =
+        if pre_loaded_merged_branches
+          pre_loaded_merged_branches.include?(branch.name)
+        else
+          ancestor?(branch.target, root_ref_sha)
+        end
 
-    if branch_commit
-      same_head = branch_commit.id == root_ref_commit.id
-      !same_head && ancestor?(branch_commit.id, root_ref_commit.id)
+      !same_head && merged
     else
       nil
     end
@@ -979,6 +986,8 @@ class Repository
     end
   end
 
+  delegate :merged_branch_names, to: :raw_repository
+
   def merge_base(first_commit_id, second_commit_id)
     first_commit_id = commit(first_commit_id).try(:id) || first_commit_id
     second_commit_id = commit(second_commit_id).try(:id) || second_commit_id

app/views/projects/branches/_branch.html.haml

+- merged = local_assigns.fetch(:merged, false)
 - commit = @repository.commit(branch.dereferenced_target)
 - bar_graph_width_factor = @max_commits > 0 ? 100.0/@max_commits : 0
 - diverging_commit_counts = @repository.diverging_commit_counts(branch)
@@ -12,7 +13,7 @@
      
     - if branch.name == @repository.root_ref
       %span.label.label-primary default
-    - elsif @repository.merged_to_root_ref? branch.name
+    - elsif merged
       %span.label.label-info.has-tooltip{ title: s_('Branches|Merged into %{default_branch}') % { default_branch: @repository.root_ref } }
         = s_('Branches|merged')
 
@@ -53,7 +54,7 @@
                 target: "#modal-delete-branch",
                 delete_path: project_branch_path(@project, branch.name),
                 branch_name: branch.name,
-                is_merged: ("true" if @repository.merged_to_root_ref?(branch.name)) } }
+                is_merged: ("true" if merged) } }
               = icon("trash-o")
           - else
             %button{ class: "btn btn-remove remove-row js-ajax-loading-spinner has-tooltip disabled",

app/views/projects/branches/index.html.haml

@@ -41,7 +41,7 @@
   - if @branches.any?
     %ul.content-list.all-branches
       - @branches.each do |branch|
-        = render "projects/branches/branch", branch: branch
+        = render "projects/branches/branch", branch: branch, merged: @repository.merged_to_root_ref?(branch, @merged_branch_names)
     = paginate @branches, theme: 'gitlab'
   - else
     .nothing-here-block

changelogs/unreleased/use-git-branch-merged.yml

+---
+title: Improve branch listing page performance
+merge_request: 14729
+author:
+type: performance

lib/gitlab/git/branch.rb

@@ -3,6 +3,14 @@
 module Gitlab
   module Git
     class Branch < Ref
+      def self.find(repo, branch_name)
+        if branch_name.is_a?(Gitlab::Git::Branch)
+          branch_name
+        else
+          repo.find_branch(branch_name)
+        end
+      end
+
       def initialize(repository, name, target, target_commit)
         super(repository, name, target, target_commit)
       end

lib/gitlab/git/repository.rb

@@ -511,6 +511,10 @@ module Gitlab
         gitaly_commit_client.ancestor?(from, to)
       end
 
+      def merged_branch_names(branch_names = [])
+        Set.new(git_merged_branch_names(branch_names))
+      end
+
       # Return an array of Diff objects that represent the diff
       # between +from+ and +to+.  See Diff::filter_diff_options for the allowed
       # diff options.  The +options+ hash can also include :break_rewrites to
@@ -1180,6 +1184,13 @@ module Gitlab
         sort_branches(branches, sort_by)
       end
 
+      def git_merged_branch_names(branch_names = [])
+        lines = run_git(['branch', '--merged', root_ref] + branch_names)
+          .first.lines
+
+        lines.map(&:strip)
+      end
+
       def log_using_shell?(options)
         options[:path].present? ||
           options[:disable_walk] ||

spec/lib/gitlab/git/branch_spec.rb

@@ -7,6 +7,38 @@ describe Gitlab::Git::Branch, seed_helper: true do
 
   it { is_expected.to be_kind_of Array }
 
+  describe '.find' do
+    subject { described_class.find(repository, branch) }
+
+    before do
+      allow(repository).to receive(:find_branch).with(branch)
+        .and_call_original
+    end
+
+    context 'when finding branch via branch name' do
+      let(:branch) { 'master' }
+
+      it 'returns a branch object' do
+        expect(subject).to be_a(described_class)
+        expect(subject.name).to eq(branch)
+
+        expect(repository).to have_received(:find_branch).with(branch)
+      end
+    end
+
+    context 'when the branch is already a branch' do
+      let(:commit) { repository.commit('master') }
+      let(:branch) { described_class.new(repository, 'master', commit.sha, commit) }
+
+      it 'returns a branch object' do
+        expect(subject).to be_a(described_class)
+        expect(subject).to eq(branch)
+
+        expect(repository).not_to have_received(:find_branch).with(branch)
+      end
+    end
+  end
+
   describe '#size' do
     subject { super().size }
     it { is_expected.to eq(SeedRepo::Repo::BRANCHES.size) }

spec/lib/gitlab/git/repository_spec.rb

@@ -1135,6 +1135,32 @@ describe Gitlab::Git::Repository, seed_helper: true do
     end
   end
 
+  describe '#merged_branch_names' do
+    context 'when branch names are passed' do
+      it 'only returns the names we are asking' do
+        names = repository.merged_branch_names(%w[merge-test])
+
+        expect(names).to contain_exactly('merge-test')
+      end
+
+      it 'does not return unmerged branch names' do
+        names = repository.merged_branch_names(%w[feature])
+
+        expect(names).to be_empty
+      end
+    end
+
+    context 'when no branch names are specified' do
+      it 'returns all merged branch names' do
+        names = repository.merged_branch_names
+
+        expect(names).to include('merge-test')
+        expect(names).to include('fix-mode')
+        expect(names).not_to include('feature')
+      end
+    end
+  end
+
   describe "#ls_files" do
     let(:master_file_paths) { repository.ls_files("master") }
     let(:not_existed_branch) { repository.ls_files("not_existed_branch") }

spec/models/repository_spec.rb

@@ -299,6 +299,24 @@ describe Repository do
 
       it { is_expected.to be_falsey }
     end
+
+    context 'when pre-loaded merged branches are provided' do
+      using RSpec::Parameterized::TableSyntax
+
+      where(:branch, :pre_loaded, :expected) do
+        'not-merged-branch' | ['branch-merged']     | false
+        'branch-merged'     | ['not-merged-branch'] | false
+        'branch-merged'     | ['branch-merged']     | true
+        'not-merged-branch' | ['not-merged-branch'] | false
+        'master'            | ['master']            | false
+      end
+
+      with_them do
+        subject { repository.merged_to_root_ref?(branch, pre_loaded) }
+
+        it { is_expected.to eq(expected) }
+      end
+    end
   end
 
   describe '#can_be_merged?' do