Add GitShallowClone feature

This feature enables the use of shallow clones when pulling source from
Git repositories.

Signed-off-by: Paulo Gomes <paulo.gomes@weave.works>

controllers/imageupdateautomation_controller.go

@@ -298,6 +298,10 @@ func (r *ImageUpdateAutomationReconciler) Reconcile(ctx context.Context, req ctr
 		opts.Branch = ref.Branch
 	}
 
+	if enabled, _ := r.features[features.GitShallowClone]; enabled {
+		opts.ShallowClone = true
+	}
+
 	// Use the git operations timeout for the repo.
 	cloneCtx, cancel := context.WithTimeout(ctx, origin.Spec.Timeout.Duration)
 	defer cancel()

internal/features/features.go

@@ -32,6 +32,10 @@ const (
 	// When enabled, libgit2 won't be initialized, nor will any git2go cgo
 	// code be called.
 	ForceGoGitImplementation = "ForceGoGitImplementation"
+
+	// GitShallowClone enables the use of shallow clones when pulling source from
+	// Git repositories.
+	GitShallowClone = "GitShallowClone"
 )
 
 var features = map[string]bool{
@@ -42,6 +46,10 @@ var features = map[string]bool{
 	// ForceGoGitImplementation
 	// opt-out from v0.27
 	ForceGoGitImplementation: true,
+
+	// GitShallowClone
+	// opt-in from v0.28
+	GitShallowClone: false,
 }
 
 // DefaultFeatureGates contains a list of all supported feature gates and