Add project level git depth setting

Introduce default_git_depth in project's CI/CD settings and set it to
50. Use it if there is no GIT_DEPTH variable specified. Apply this
default only to newly created projects and keep it nil for old ones
in order to not break pipelines that rely on non-shallow clones.

default_git_depth can be updated from CI/CD Settings in the UI, must be
either nil or integer between 0 and 1000 (incl).

Inherit default_git_depth from the origin project when forking projects.

MR pipelines are run on a MR ref (refs/merge-requests/:iid/merge) and it
contains unique commit (i.e. merge commit) which doesn't exist in the
other branch/tags refs. We need to add it cause otherwise it may break
pipelines for old projects that have already enabled Pipelines for merge
results and have git depth 0.

Document new default_git_depth project CI/CD setting

8 files changed, 104 insertions, 26 deletions

diff --git a/spec/controllers/projects/settings/ci_cd_controller_spec.rb b/spec/controllers/projects/settings/ci_cd_controller_spec.rb
index b91a4df40a5..117b9cf7915 100644
--- a/spec/controllers/projects/settings/ci_cd_controller_spec.rb
+++ b/spec/controllers/projects/settings/ci_cd_controller_spec.rb
@@ -200,6 +200,21 @@ describe Projects::Settings::CiCdController do
           expect(response).to redirect_to(namespace_project_settings_ci_cd_path)
         end
       end
+
+      context 'when default_git_depth is not specified' do
+        let(:params) { { ci_cd_settings_attributes: { default_git_depth: 10 } } }
+
+        before do
+          project.ci_cd_settings.update!(default_git_depth: nil)
+        end
+
+        it 'set specified git depth' do
+          subject
+
+          project.reload
+          expect(project.default_git_depth).to eq(10)
+        end
+      end
     end
   end
 end
diff --git a/spec/lib/gitlab/background_migration/delete_diff_files_spec.rb b/spec/lib/gitlab/background_migration/delete_diff_files_spec.rb
index 27281333348..22ec09d44ac 100644
--- a/spec/lib/gitlab/background_migration/delete_diff_files_spec.rb
+++ b/spec/lib/gitlab/background_migration/delete_diff_files_spec.rb
@@ -3,6 +3,12 @@ require 'spec_helper'
 # rubocop:disable RSpec/FactoriesInMigrationSpecs
 describe Gitlab::BackgroundMigration::DeleteDiffFiles, :migration, :sidekiq, schema: 20180619121030 do
   describe '#perform' do
+    before do
+      # This migration was created before we introduced ProjectCiCdSetting#default_git_depth
+      allow_any_instance_of(ProjectCiCdSetting).to receive(:default_git_depth?).and_return(true)
+      allow_any_instance_of(ProjectCiCdSetting).to receive(:default_git_depth).and_return(nil)
+    end
+
     context 'when diff files can be deleted' do
       let(:merge_request) { create(:merge_request, :merged) }
       let!(:merge_request_diff) do
diff --git a/spec/lib/gitlab/background_migration/populate_external_pipeline_source_spec.rb b/spec/lib/gitlab/background_migration/populate_external_pipeline_source_spec.rb
index 3e009fed0f1..317745bcf83 100644
--- a/spec/lib/gitlab/background_migration/populate_external_pipeline_source_spec.rb
+++ b/spec/lib/gitlab/background_migration/populate_external_pipeline_source_spec.rb
@@ -9,6 +9,9 @@ describe Gitlab::BackgroundMigration::PopulateExternalPipelineSource, :migration
   before do
     # This migration was created before we introduced metadata configs
     stub_feature_flags(ci_build_metadata_config: false)
+    # This migration was created before we introduced ProjectCiCdSetting#default_git_depth
+    allow_any_instance_of(ProjectCiCdSetting).to receive(:default_git_depth?).and_return(true)
+    allow_any_instance_of(ProjectCiCdSetting).to receive(:default_git_depth).and_return(nil)
   end
 
   let!(:internal_pipeline) { create(:ci_pipeline, source: :web) }
diff --git a/spec/migrations/remove_orphaned_label_links_spec.rb b/spec/migrations/remove_orphaned_label_links_spec.rb
index 13b8919343e..4c8135cd08c 100644
--- a/spec/migrations/remove_orphaned_label_links_spec.rb
+++ b/spec/migrations/remove_orphaned_label_links_spec.rb
@@ -10,6 +10,12 @@ describe RemoveOrphanedLabelLinks, :migration do
   let(:project) { create(:project) } # rubocop:disable RSpec/FactoriesInMigrationSpecs
   let(:label) { create_label }
 
+  before do
+    # This migration was created before we introduced ProjectCiCdSetting#default_git_depth
+    allow_any_instance_of(ProjectCiCdSetting).to receive(:default_git_depth?).and_return(true)
+    allow_any_instance_of(ProjectCiCdSetting).to receive(:default_git_depth).and_return(nil)
+  end
+
   context 'add foreign key on label_id' do
     let!(:label_link_with_label) { create_label_link(label_id: label.id) }
     let!(:label_link_without_label) { create_label_link(label_id: nil) }
diff --git a/spec/models/project_ci_cd_setting_spec.rb b/spec/models/project_ci_cd_setting_spec.rb
index 4aa62028169..80f75f45e43 100644
--- a/spec/models/project_ci_cd_setting_spec.rb
+++ b/spec/models/project_ci_cd_setting_spec.rb
@@ -21,4 +21,26 @@ describe ProjectCiCdSetting do
       2.times { described_class.available? }
     end
   end
+
+  describe 'validations' do
+    it { is_expected.to validate_numericality_of(:default_git_depth).only_integer.is_greater_than_or_equal_to(0).is_less_than_or_equal_to(1000).allow_nil }
+  end
+
+  describe '#default_git_depth' do
+    let(:default_value) { described_class::DEFAULT_GIT_DEPTH }
+
+    it 'sets default value for new records' do
+      project = create(:project)
+
+      expect(project.ci_cd_settings.default_git_depth).to eq(default_value)
+    end
+
+    it 'does not set default value if present' do
+      project = build(:project)
+      project.build_ci_cd_settings(default_git_depth: 42)
+      project.save!
+
+      expect(project.reload.ci_cd_settings.default_git_depth).to eq(42)
+    end
+  end
 end
diff --git a/spec/presenters/ci/build_runner_presenter_spec.rb b/spec/presenters/ci/build_runner_presenter_spec.rb
index 3430111ca9e..9ed8e3a4e0a 100644
--- a/spec/presenters/ci/build_runner_presenter_spec.rb
+++ b/spec/presenters/ci/build_runner_presenter_spec.rb
@@ -119,23 +119,23 @@ describe Ci::BuildRunnerPresenter do
   end
 
   describe '#git_depth' do
-    subject { presenter.git_depth }
-
     let(:build) { create(:ci_build) }
 
-    it 'returns the correct git depth' do
-      is_expected.to eq(0)
-    end
+    subject(:git_depth) { presenter.git_depth }
 
     context 'when GIT_DEPTH variable is specified' do
       before do
         create(:ci_pipeline_variable, key: 'GIT_DEPTH', value: 1, pipeline: build.pipeline)
       end
 
-      it 'returns the correct git depth' do
-        is_expected.to eq(1)
+      it 'returns its value' do
+        expect(git_depth).to eq(1)
       end
     end
+
+    it 'defaults to git depth setting for the project' do
+      expect(git_depth).to eq(build.project.default_git_depth)
+    end
   end
 
   describe '#refspecs' do
@@ -144,24 +144,24 @@ describe Ci::BuildRunnerPresenter do
     let(:build) { create(:ci_build) }
 
     it 'returns the correct refspecs' do
-      is_expected.to contain_exactly('+refs/tags/*:refs/tags/*',
-                                     '+refs/heads/*:refs/remotes/origin/*')
+      is_expected.to contain_exactly("+refs/heads/#{build.ref}:refs/remotes/origin/#{build.ref}")
     end
 
-    context 'when GIT_DEPTH variable is specified' do
-      before do
-        create(:ci_pipeline_variable, key: 'GIT_DEPTH', value: 1, pipeline: build.pipeline)
-      end
+    context 'when ref is tag' do
+      let(:build) { create(:ci_build, :tag) }
 
       it 'returns the correct refspecs' do
-        is_expected.to contain_exactly("+refs/heads/#{build.ref}:refs/remotes/origin/#{build.ref}")
+        is_expected.to contain_exactly("+refs/tags/#{build.ref}:refs/tags/#{build.ref}")
       end
 
-      context 'when ref is tag' do
-        let(:build) { create(:ci_build, :tag) }
+      context 'when GIT_DEPTH is zero' do
+        before do
+          create(:ci_pipeline_variable, key: 'GIT_DEPTH', value: 0, pipeline: build.pipeline)
+        end
 
         it 'returns the correct refspecs' do
-          is_expected.to contain_exactly("+refs/tags/#{build.ref}:refs/tags/#{build.ref}")
+          is_expected.to contain_exactly('+refs/tags/*:refs/tags/*',
+                                         '+refs/heads/*:refs/remotes/origin/*')
         end
       end
     end
@@ -173,17 +173,27 @@ describe Ci::BuildRunnerPresenter do
 
       it 'returns the correct refspecs' do
         is_expected
-          .to contain_exactly('+refs/heads/*:refs/remotes/origin/*',
-                              '+refs/tags/*:refs/tags/*',
-                              '+refs/merge-requests/1/head:refs/merge-requests/1/head')
+          .to contain_exactly('+refs/merge-requests/1/head:refs/merge-requests/1/head')
+      end
+
+      context 'when GIT_DEPTH is zero' do
+        before do
+          create(:ci_pipeline_variable, key: 'GIT_DEPTH', value: 0, pipeline: build.pipeline)
+        end
+
+        it 'returns the correct refspecs' do
+          is_expected
+            .to contain_exactly('+refs/merge-requests/1/head:refs/merge-requests/1/head',
+                                '+refs/heads/*:refs/remotes/origin/*',
+                                '+refs/tags/*:refs/tags/*')
+        end
       end
 
       context 'when pipeline is legacy detached merge request pipeline' do
         let(:merge_request) { create(:merge_request, :with_legacy_detached_merge_request_pipeline) }
 
         it 'returns the correct refspecs' do
-          is_expected.to contain_exactly('+refs/tags/*:refs/tags/*',
-                                         '+refs/heads/*:refs/remotes/origin/*')
+          is_expected.to contain_exactly("+refs/heads/#{build.ref}:refs/remotes/origin/#{build.ref}")
         end
       end
     end
diff --git a/spec/requests/api/runner_spec.rb b/spec/requests/api/runner_spec.rb
index 3202050ac20..038c958b5cc 100644
--- a/spec/requests/api/runner_spec.rb
+++ b/spec/requests/api/runner_spec.rb
@@ -444,8 +444,8 @@ describe API::Runner, :clean_gitlab_redis_shared_state do
               'sha' => job.sha,
               'before_sha' => job.before_sha,
               'ref_type' => 'branch',
-              'refspecs' => %w[+refs/heads/*:refs/remotes/origin/* +refs/tags/*:refs/tags/*],
-              'depth' => 0 }
+              'refspecs' => ["+refs/heads/#{job.ref}:refs/remotes/origin/#{job.ref}"],
+              'depth' => project.default_git_depth }
           end
 
           let(:expected_steps) do
@@ -531,7 +531,11 @@ describe API::Runner, :clean_gitlab_redis_shared_state do
               end
             end
 
-            context 'when GIT_DEPTH is not specified' do
+            context 'when GIT_DEPTH is not specified and there is no default git depth for the project' do
+              before do
+                project.update!(default_git_depth: nil)
+              end
+
               it 'specifies refspecs' do
                 request_job
 
@@ -587,7 +591,11 @@ describe API::Runner, :clean_gitlab_redis_shared_state do
               end
             end
 
-            context 'when GIT_DEPTH is not specified' do
+            context 'when GIT_DEPTH is not specified and there is no default git depth for the project' do
+              before do
+                project.update!(default_git_depth: nil)
+              end
+
               it 'specifies refspecs' do
                 request_job
 
diff --git a/spec/services/projects/fork_service_spec.rb b/spec/services/projects/fork_service_spec.rb
index ec3f1782e8f..e8a38287a63 100644
--- a/spec/services/projects/fork_service_spec.rb
+++ b/spec/services/projects/fork_service_spec.rb
@@ -145,6 +145,14 @@ describe Projects::ForkService do
         end
       end
 
+      context "CI/CD settings" do
+        it "inherits default_git_depth from the origin project" do
+          @from_project.update(default_git_depth: 42)
+          @to_project = fork_project(@from_project, @to_user)
+          expect(@to_project.default_git_depth).to eq(42)
+        end
+      end
+
       context "when project has restricted visibility level" do
         context "and only one visibility level is restricted" do
           before do