1 files changed, 69 insertions, 0 deletions
diff --git a/lib/gitlab/changelog/committer.rb b/lib/gitlab/changelog/committer.rb
new file mode 100644
index 00000000000..31661650eff
--- /dev/null
+++ b/lib/gitlab/changelog/committer.rb
@@ -0,0 +1,69 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Changelog
+    # A class used for committing a release's changelog to a Git repository.
+    class Committer
+      def initialize(project, user)
+        @project = project
+        @user = user
+      end
+
+      # Commits a release's changelog to a file on a branch.
+      #
+      # The `release` argument is a `Gitlab::Changelog::Release` for which to
+      # update the changelog.
+      #
+      # The `file` argument specifies the path to commit the changes to.
+      #
+      # The `branch` argument specifies the branch to commit the changes on.
+      #
+      # The `message` argument specifies the commit message to use.
+      def commit(release:, file:, branch:, message:)
+        # When retrying, we need to reprocess the existing changelog from
+        # scratch, otherwise we may end up throwing away changes. As such, all
+        # the logic is contained within the retry block.
+        Retriable.retriable(on: Error) do
+          commit = Gitlab::Git::Commit.last_for_path(
+            @project.repository,
+            branch,
+            file,
+            literal_pathspec: true
+          )
+
+          content = blob_content(file, commit)
+
+          # If the release has already been added (e.g. concurrently by another
+          # API call), we don't want to add it again.
+          break if content&.match?(release.header_start_pattern)
+
+          service = Files::MultiService.new(
+            @project,
+            @user,
+            commit_message: message,
+            branch_name: branch,
+            start_branch: branch,
+            actions: [
+              {
+                action: content ? 'update' : 'create',
+                content: Generator.new(content.to_s).add(release),
+                file_path: file,
+                last_commit_id: commit&.sha
+              }
+            ]
+          )
+
+          result = service.execute
+
+          raise Error.new(result[:message]) if result[:status] != :success
+        end
+      end
+
+      def blob_content(file, commit = nil)
+        return unless commit
+
+        @project.repository.blob_at(commit.sha, file)&.data
+      end
+    end
+  end
+end