github.com/containers/podman/v5@v5.1.0-rc1/docs/source/markdown/options/env-merge.md (about)

     1  ####> This option file is used in:
     2  ####>   podman create, run
     3  ####> If file is edited, make sure the changes
     4  ####> are applicable to all of those.
     5  #### **--env-merge**=*env*
     6  
     7  Preprocess default environment variables for the containers. For example
     8  if image contains environment variable `hello=world` user can preprocess
     9  it using `--env-merge hello=${hello}-some` so new value is `hello=world-some`.
    10  
    11  Please note that if the environment variable `hello` is not present in the image,
    12  then it'll be replaced by an empty string and so using `--env-merge hello=${hello}-some`
    13  would result in the new value of `hello=-some`, notice the leading `-` delimiter.