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

1 files changed, 15 insertions, 0 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