Combining saved parameter overrides (toml/yaml file) with --parameter-overrides on the CLI

[mbklein]

I have a project that has both persistent parameters and per-deploy parameters (e.g., one of the lambda functions has to have the current commit hash as an environment variable for error reporting reasons). However, I've noticed that when I use the --parameter-overrides command line argument, it completely ignores the parameter_overrides section of my samconfig.yaml file. I would have expected sam deploy to merge parameter values in “immediacy” order, such as:

1. Command line --parameter-overrides have highest precedence
2. samconfig.{toml,yaml} parameter_overrides have next highest precedence
3. Default values have lowest precedence

Is there a way I can achieve what I'm trying to do without either adding ephemeral values to my config file or putting all overrides on the command line?