Add endpoint for fetching diverging commit counts

Extract diverging_commit_counts into a service class

1 files changed, 54 insertions, 0 deletions

diff --git a/app/services/branches/diverging_commit_counts_service.rb b/app/services/branches/diverging_commit_counts_service.rb
new file mode 100644
index 00000000000..f947cec1663
--- /dev/null
+++ b/app/services/branches/diverging_commit_counts_service.rb
@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+module Branches
+  class DivergingCommitCountsService
+    def initialize(repository)
+      @repository = repository
+      @cache = Gitlab::RepositoryCache.new(repository)
+    end
+
+    def call(branch)
+      if Feature.enabled?('gitaly_count_diverging_commits_no_max')
+        diverging_commit_counts_without_max(branch)
+      else
+        diverging_commit_counts(branch)
+      end
+    end
+
+    private
+
+    attr_reader :repository, :cache
+
+    delegate :raw_repository, to: :repository
+
+    def diverging_commit_counts(branch)
+      ## TODO: deprecate the below code after 12.0
+      @root_ref_hash ||= raw_repository.commit(repository.root_ref).id
+      cache.fetch(:"diverging_commit_counts_#{branch.name}") do
+        number_commits_behind, number_commits_ahead =
+          repository.raw_repository.diverging_commit_count(
+            @root_ref_hash,
+            branch.dereferenced_target.sha,
+            max_count: Repository::MAX_DIVERGING_COUNT)
+
+        if number_commits_behind + number_commits_ahead >= Repository::MAX_DIVERGING_COUNT
+          { distance: Repository::MAX_DIVERGING_COUNT }
+        else
+          { behind: number_commits_behind, ahead: number_commits_ahead }
+        end
+      end
+    end
+
+    def diverging_commit_counts_without_max(branch)
+      @root_ref_hash ||= raw_repository.commit(repository.root_ref).id
+      cache.fetch(:"diverging_commit_counts_without_max_#{branch.name}") do
+        number_commits_behind, number_commits_ahead =
+          raw_repository.diverging_commit_count(
+            @root_ref_hash,
+            branch.dereferenced_target.sha)
+
+        { behind: number_commits_behind, ahead: number_commits_ahead }
+      end
+    end
+  end
+end