symfony - How to update symfony2/doctrine model files when database is being managed externally -

i apologize if overly-subjective or broad.

i'm handling symfony2 app using doctrine orm. issue database managed entirely externally. so, creating model files not issue, best way of handling structural changes , additions going forward? unlike symfony1 , other orm's, symfony 2 , 3 don't provide built-in functionality ongoing , safe regeneration of model files.

in symfony 1, handled with:

symfony doctrine:build-schema

symfony doctrine:build-model

symfony doctrine:build-forms

etc...

however now, if database changed , regenerate model files, existing ones overwritten. main issues here one, users model modified add in of authentication , other methods used symfony. models need manually changed accommodate relationships. additionally it's far easier handle validation through model files, such using validation groups, rather in every individual form.

is there best way handle in symfony2+? seems cumbersome have manually merge model files if regenerated.