Add submodule update API endpoint

This new endpoint allow users to update a submodule's reference.

The MR involves adding a new operation RPC operation in gitaly-proto
(see gitlab-org/gitaly-proto!233) and change Gitaly to use this
new version (see gitlab-org/gitaly!936).

See gitlab-org/gitlab-ce!20949

2 files changed, 50 insertions, 0 deletions

diff --git a/app/models/repository.rb b/app/models/repository.rb
index ee5579329a8..6e179f61a7b 100644
--- a/app/models/repository.rb
+++ b/app/models/repository.rb
@@ -1014,6 +1014,18 @@ class Repository
                                        message: merge_request.title)
   end
 
+  def update_submodule(user, submodule, commit_sha, message:, branch:)
+    with_cache_hooks do
+      raw.update_submodule(
+        user: user,
+        submodule: submodule,
+        commit_sha: commit_sha,
+        branch: branch,
+        message: message
+      )
+    end
+  end
+
   def blob_data_at(sha, path)
     blob = blob_at(sha, path)
     return unless blob
diff --git a/app/services/submodules/update_service.rb b/app/services/submodules/update_service.rb
new file mode 100644
index 00000000000..a6011a920bd
--- /dev/null
+++ b/app/services/submodules/update_service.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+module Submodules
+  class UpdateService < Commits::CreateService
+    include Gitlab::Utils::StrongMemoize
+
+    def initialize(*args)
+      super
+
+      @start_branch = @branch_name
+      @commit_sha = params[:commit_sha].presence
+      @submodule = params[:submodule].presence
+      @commit_message = params[:commit_message].presence || "Update submodule #{@submodule} with oid #{@commit_sha}"
+    end
+
+    def validate!
+      super
+
+      raise ValidationError, 'The repository is empty' if repository.empty?
+    end
+
+    def execute
+      super
+    rescue StandardError => e
+      error(e.message)
+    end
+
+    def create_commit!
+      repository.update_submodule(current_user,
+                                  @submodule,
+                                  @commit_sha,
+                                  message: @commit_message,
+                                  branch: @branch_name)
+    rescue ArgumentError, TypeError
+      raise ValidationError, 'Invalid parameters'
+    end
+  end
+end