* Move setting of default EnvVarFormat to the Prepare function
* Add generated hcl2 structure for the updated Shell provisioner config
* Move `EnvVarFormat` field to shared common shell type
* Add description for the `env_var_format` parameter
* Update `env_var_format` when used with `use_env_var_file`
It is simply the best/simplest solution and trying to prevent users from passing and integer here would be like opening a can of worms. Because:
* we cannot make mapstructure validate our duration string ( with an UnmarshalJSON func etc.)
* we cannot make mapstructure spit a string instead of a duration and packer will decode-encode-decode config.
* the hcl2 generated code asks for a string, so this will be enforced by default.
nywilken
Adrien Delorme