Rename from base to start because base could mean merge base

app/controllers/concerns/creates_commit.rb

app/models/repository.rb

app/services/commits/change_service.rb

app/services/compare_service.rb

app/services/files/base_service.rb

app/services/files/create_dir_service.rb

app/services/files/create_service.rb

app/services/files/delete_service.rb

app/services/files/multi_service.rb

app/services/files/update_service.rb

app/services/git_operation_service.rb