Support for passing existing environments in project spec file for update command

[abhijeetkaurav1st]

calm update project -f <project_file>. command update the project with the file data. All data is overrided as of now.
Need a way to pass existing environments in project file.
Ex:

class Project1(Project):
     envs = [Env1, Env2]
     env_refs = [Ref.Environment("Existing environment with this project")]

Where env_refs will take existing environments to be remain in the project

[abhijeetkaurav1st]

Or much better, if during update we will not remove existing envs from project also.

[glover-chris]

Agree with your above better comment. We use separate environment files and do not create envs within the project file. Maybe a switch at project update which will not remove existing? Also a switch to ensure users/groups are not removed from the project if not included in the project.py file (most customers want to separate their envs and users/groups from the project file in order to keep them as atomic as possible.