`Ref` objects receive the `canonical_name` from Rugged

The `Gitlab::Git::Ref` initializer, which `Branch` inherits, already
removes the `refs/heads|tags/` prefix from the provided name via
`Gitlab::Git.ref_name`, so there should be no functional difference to
providing the "canonical name".

In a future commit, we'll store the canonical name in addition to the
non-prefixed name.

10 files changed, 117 insertions, 57 deletions

diff --git a/changelogs/unreleased/rs-divergent-refs-response.yml b/changelogs/unreleased/rs-divergent-refs-response.yml
new file mode 100644
index 000000000..e85e96ecf
--- /dev/null
+++ b/changelogs/unreleased/rs-divergent-refs-response.yml
@@ -0,0 +1,5 @@
+---
+title: Add DivergentRefs to UpdateRemoteMirrorResponse
+merge_request: 2028
+author:
+type: added
diff --git a/internal/service/remote/update_remote_mirror_test.go b/internal/service/remote/update_remote_mirror_test.go
index 499c40b13..5242fc0df 100644
--- a/internal/service/remote/update_remote_mirror_test.go
+++ b/internal/service/remote/update_remote_mirror_test.go
@@ -223,8 +223,9 @@ func TestSuccessfulUpdateRemoteMirrorRequestWithKeepDivergentRefs(t *testing.T)
 	require.NoError(t, err)
 	require.NoError(t, stream.Send(firstRequest))
 
-	_, err = stream.CloseAndRecv()
+	response, err := stream.CloseAndRecv()
 	require.NoError(t, err)
+	require.ElementsMatch(t, response.DivergentRefs, [][]byte{[]byte("refs/heads/master")})
 
 	mirrorRefs := string(testhelper.MustRunCommand(t, nil, "git", "-C", mirrorPath, "for-each-ref"))
 
diff --git a/proto/go/gitalypb/remote.pb.go b/proto/go/gitalypb/remote.pb.go
index 9ac3909f5..68b26f61e 100644
--- a/proto/go/gitalypb/remote.pb.go
+++ b/proto/go/gitalypb/remote.pb.go
@@ -371,6 +371,7 @@ func (m *UpdateRemoteMirrorRequest) GetKeepDivergentRefs() bool {
 }
 
 type UpdateRemoteMirrorResponse struct {
+	DivergentRefs        [][]byte `protobuf:"bytes,1,rep,name=divergent_refs,json=divergentRefs,proto3" json:"divergent_refs,omitempty"`
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`
 	XXX_unrecognized     []byte   `json:"-"`
 	XXX_sizecache        int32    `json:"-"`
@@ -401,6 +402,13 @@ func (m *UpdateRemoteMirrorResponse) XXX_DiscardUnknown() {
 
 var xxx_messageInfo_UpdateRemoteMirrorResponse proto.InternalMessageInfo
 
+func (m *UpdateRemoteMirrorResponse) GetDivergentRefs() [][]byte {
+	if m != nil {
+		return m.DivergentRefs
+	}
+	return nil
+}
+
 type FindRemoteRepositoryRequest struct {
 	Remote               string   `protobuf:"bytes,1,opt,name=remote,proto3" json:"remote,omitempty"`
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`
@@ -721,55 +729,56 @@ func init() {
 func init() { proto.RegisterFile("remote.proto", fileDescriptor_eefc82927d57d89b) }
 
 var fileDescriptor_eefc82927d57d89b = []byte{
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+	0x95, 0x08, 0x00, 0x00,
 }
 
 // Reference imports to suppress errors if they are not otherwise used.
diff --git a/proto/remote.proto b/proto/remote.proto
index 624f826fd..67cb012f8 100644
--- a/proto/remote.proto
+++ b/proto/remote.proto
@@ -87,7 +87,9 @@ message UpdateRemoteMirrorRequest {
   bool keep_divergent_refs = 6;
 }
 
-message UpdateRemoteMirrorResponse {}
+message UpdateRemoteMirrorResponse {
+  repeated bytes divergent_refs = 1;
+}
 
 message FindRemoteRepositoryRequest {
   string remote = 1;
diff --git a/ruby/lib/gitaly_server/remote_service.rb b/ruby/lib/gitaly_server/remote_service.rb
index fa62ec092..66a2d6b7d 100644
--- a/ruby/lib/gitaly_server/remote_service.rb
+++ b/ruby/lib/gitaly_server/remote_service.rb
@@ -2,6 +2,9 @@ module GitalyServer
   class RemoteService < Gitaly::RemoteService::Service
     include Utils
 
+    # Maximum number of divergent refs to return in UpdateRemoteMirrorResponse
+    DIVERGENT_REF_LIMIT = 100
+
     def add_remote(request, call)
       repo = Gitlab::Git::Repository.from_gitaly(request.repository, call)
 
@@ -38,7 +41,9 @@ module GitalyServer
 
       remote_mirror.update
 
-      Gitaly::UpdateRemoteMirrorResponse.new
+      Gitaly::UpdateRemoteMirrorResponse.new(
+        divergent_refs: remote_mirror.divergent_refs.take(DIVERGENT_REF_LIMIT)
+      )
     end
   end
 end
diff --git a/ruby/lib/gitlab/git/ref.rb b/ruby/lib/gitlab/git/ref.rb
index fdf35e473..e45bec404 100644
--- a/ruby/lib/gitlab/git/ref.rb
+++ b/ruby/lib/gitlab/git/ref.rb
@@ -5,6 +5,9 @@ module Gitlab
     class Ref
       include Gitlab::EncodingHelper
 
+      # Canonical refname, including `refs/heads|tags/` prefix
+      attr_reader :refname
+
       # Branch or tag name
       # without "refs/tags|heads" prefix
       attr_reader :name
@@ -34,6 +37,7 @@ module Gitlab
       end
 
       def initialize(_repository, name, target, dereferenced_target)
+        @refname = name
         @name = Gitlab::Git.ref_name(name)
         @dereferenced_target = dereferenced_target
         @target = if target.respond_to?(:oid)
diff --git a/ruby/lib/gitlab/git/remote_mirror.rb b/ruby/lib/gitlab/git/remote_mirror.rb
index 2ad02bb26..02a35026d 100644
--- a/ruby/lib/gitlab/git/remote_mirror.rb
+++ b/ruby/lib/gitlab/git/remote_mirror.rb
@@ -3,12 +3,19 @@ module Gitlab
     class RemoteMirror
       attr_reader :repository, :remote_name, :ssh_auth, :only_branches_matching
 
+      # An Array of local refnames that have diverged on the remote
+      #
+      # Only populated when `keep_divergent_refs` is enabled
+      attr_reader :divergent_refs
+
       def initialize(repository, remote_name, ssh_auth:, only_branches_matching:, keep_divergent_refs:)
         @repository = repository
         @remote_name = remote_name
         @ssh_auth = ssh_auth
         @only_branches_matching = only_branches_matching
         @keep_divergent_refs = keep_divergent_refs
+
+        @divergent_refs = []
       end
 
       def update
@@ -71,7 +78,12 @@ module Gitlab
             false
           elsif @keep_divergent_refs
             # Mirror the ref if its remote counterpart hasn't diverged
-            repository.ancestor?(remote_target&.id, local_target&.id)
+            if repository.ancestor?(remote_target&.id, local_target&.id)
+              true
+            else
+              @divergent_refs << ref.refname
+              false
+            end
           else
             # Attempt to overwrite whatever's on the remote; push rules and
             # protected branches may still prevent this
diff --git a/ruby/lib/gitlab/git/repository.rb b/ruby/lib/gitlab/git/repository.rb
index 326c4c563..80b4c24ef 100644
--- a/ruby/lib/gitlab/git/repository.rb
+++ b/ruby/lib/gitlab/git/repository.rb
@@ -181,7 +181,7 @@ module Gitlab
 
           target_commit = Gitlab::Git::Commit.find(self, ref.target)
           Gitlab::Git::Tag.new(self,
-                               name: ref.name,
+                               name: ref.canonical_name,
                                target: ref.target,
                                target_commit: target_commit,
                                message: message)
@@ -543,7 +543,7 @@ module Gitlab
         rugged_ref = rugged.branches[name]
         if rugged_ref
           target_commit = Gitlab::Git::Commit.find(self, rugged_ref.target)
-          Gitlab::Git::Branch.new(self, rugged_ref.name, rugged_ref.target, target_commit)
+          Gitlab::Git::Branch.new(self, rugged_ref.canonical_name, rugged_ref.target, target_commit)
         end
       end
 
@@ -552,7 +552,7 @@ module Gitlab
 
         return unless rugged_ref
 
-        Gitlab::Git::Ref.new(self, rugged_ref.name, rugged_ref.target, rugged_ref.target_id)
+        Gitlab::Git::Ref.new(self, rugged_ref.canonical_name, rugged_ref.target, rugged_ref.target_id)
       end
 
       # Delete the specified branch from the repository
@@ -798,7 +798,7 @@ module Gitlab
         branches = rugged.branches.each(filter).map do |rugged_ref|
           begin
             target_commit = Gitlab::Git::Commit.find(self, rugged_ref.target)
-            Gitlab::Git::Branch.new(self, rugged_ref.name, rugged_ref.target, target_commit)
+            Gitlab::Git::Branch.new(self, rugged_ref.canonical_name, rugged_ref.target, target_commit)
           rescue Rugged::ReferenceError
             # Omit invalid branch
           end
diff --git a/ruby/proto/gitaly/remote_pb.rb b/ruby/proto/gitaly/remote_pb.rb
index 6f03c83a4..36f985412 100644
--- a/ruby/proto/gitaly/remote_pb.rb
+++ b/ruby/proto/gitaly/remote_pb.rb
@@ -38,6 +38,7 @@ Google::Protobuf::DescriptorPool.generated_pool.build do
       optional :keep_divergent_refs, :bool, 6
     end
     add_message "gitaly.UpdateRemoteMirrorResponse" do
+      repeated :divergent_refs, :bytes, 1
     end
     add_message "gitaly.FindRemoteRepositoryRequest" do
       optional :remote, :string, 1
diff --git a/ruby/spec/lib/gitaly_server/remote_service_spec.rb b/ruby/spec/lib/gitaly_server/remote_service_spec.rb
new file mode 100644
index 000000000..511b4f008
--- /dev/null
+++ b/ruby/spec/lib/gitaly_server/remote_service_spec.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe GitalyServer::RemoteService do
+  describe '#update_remote_mirror' do
+    it 'assigns a limited number of divergent refs' do
+      stub_const("#{described_class}::DIVERGENT_REF_LIMIT", 2)
+
+      mirror = double(
+        divergent_refs: %w[refs/heads/master refs/heads/develop refs/heads/stable]
+      ).as_null_object
+      stub_const('Gitlab::Git::RemoteMirror', mirror)
+
+      call = double(to_a: [], to_ary: []).as_null_object
+      response = described_class.new.update_remote_mirror(call)
+
+      expect(response.divergent_refs).to eq(%w[refs/heads/master refs/heads/develop])
+    end
+  end
+end