Upgrade Gitaly gem and fix UserSquash RPC usage

Gitaly v1.84.0 removes the branch parameter from the UserSquash RPC in
https://gitlab.com/gitlab-org/gitaly/merge_requests/1786 because the
target branch isn't actually relevant to squash. Only the start and end
SHA matter here because squash is concerned primarily about collapsing
commits from the source, not target, branch.

Gemfile

@@ -456,7 +456,7 @@ group :ed25519 do
 end
 
 # Gitaly GRPC protocol definitions
-gem 'gitaly', '~> 1.86.0'
+gem 'gitaly', '~> 12.9.0.pre.rc4'
 
 gem 'grpc', '~> 1.24.0'
 

Gemfile.lock

@@ -366,7 +366,7 @@ GEM
       po_to_json (>= 1.0.0)
       rails (>= 3.2.0)
     git (1.5.0)
-    gitaly (1.86.0)
+    gitaly (12.9.0.pre.rc4)
       grpc (~> 1.0)
     github-markup (1.7.0)
     gitlab-chronic (0.10.5)
@@ -1228,7 +1228,7 @@ DEPENDENCIES
   gettext (~> 3.2.2)
   gettext_i18n_rails (~> 1.8.0)
   gettext_i18n_rails_js (~> 1.3)
-  gitaly (~> 1.86.0)
+  gitaly (~> 12.9.0.pre.rc4)
   github-markup (~> 1.7.0)
   gitlab-chronic (~> 0.10.5)
   gitlab-derailed_benchmarks

app/models/repository.rb

@@ -1061,8 +1061,7 @@ class Repository
   end
 
   def squash(user, merge_request, message)
-    raw.squash(user, merge_request.id, branch: merge_request.target_branch,
-                                       start_sha: merge_request.diff_start_sha,
+    raw.squash(user, merge_request.id, start_sha: merge_request.diff_start_sha,
                                        end_sha: merge_request.diff_head_sha,
                                        author: merge_request.author,
                                        message: message)

changelogs/unreleased/pokstad1-remove-branch-user-squash.yml

+---
+title: Upgrade Gitaly gem and fix UserSquash RPC usage
+merge_request: 27372
+author:
+type: other

lib/gitlab/git/repository.rb

@@ -842,10 +842,9 @@ module Gitlab
         end
       end
 
-      def squash(user, squash_id, branch:, start_sha:, end_sha:, author:, message:)
+      def squash(user, squash_id, start_sha:, end_sha:, author:, message:)
         wrapped_gitaly_errors do
-          gitaly_operation_client.user_squash(user, squash_id, branch,
-              start_sha, end_sha, author, message)
+          gitaly_operation_client.user_squash(user, squash_id, start_sha, end_sha, author, message)
         end
       end
 

lib/gitlab/gitaly_client/operation_service.rb

@@ -248,12 +248,11 @@ module Gitlab
         request_enum.close
       end
 
-      def user_squash(user, squash_id, branch, start_sha, end_sha, author, message)
+      def user_squash(user, squash_id, start_sha, end_sha, author, message)
         request = Gitaly::UserSquashRequest.new(
           repository: @gitaly_repo,
           user: Gitlab::Git::User.from_gitlab(user).to_gitaly,
           squash_id: squash_id.to_s,
-          branch: encode_binary(branch),
           start_sha: start_sha,
           end_sha: end_sha,
           author: Gitlab::Git::User.from_gitlab(author).to_gitaly,

spec/lib/gitlab/gitaly_client/operation_service_spec.rb

@@ -274,7 +274,6 @@ describe Gitlab::GitalyClient::OperationService do
   end
 
   describe '#user_squash' do
-    let(:branch_name) { 'my-branch' }
     let(:squash_id) { '1' }
     let(:start_sha) { 'b83d6e391c22777fca1ed3012fce84f633d7fed0' }
     let(:end_sha) { '54cec5282aa9f21856362fe321c800c236a61615' }
@@ -284,7 +283,6 @@ describe Gitlab::GitalyClient::OperationService do
         repository: repository.gitaly_repository,
         user: gitaly_user,
         squash_id: squash_id.to_s,
-        branch: branch_name,
         start_sha: start_sha,
         end_sha: end_sha,
         author: gitaly_user,
@@ -295,7 +293,7 @@ describe Gitlab::GitalyClient::OperationService do
     let(:response) { Gitaly::UserSquashResponse.new(squash_sha: squash_sha) }
 
     subject do
-      client.user_squash(user, squash_id, branch_name, start_sha, end_sha, user, commit_message)
+      client.user_squash(user, squash_id, start_sha, end_sha, user, commit_message)
     end
 
     it 'sends a user_squash message and returns the squash sha' do