Are declarative app configs worth it?

[Sergey Trofimov <sarg@sarg.org.ru>]

Hi guix,

I want to start a discussion around how to manage user app config 
files.
Copying my message from https://issues.guix.gnu.org/68010, where 
home-zathura-configuration with 76 fields is proposed.

I have mixed feelings about pulling 3rd-party software 
configurations in guix:
- adding it to guix increases maintenance burden: new versions 
  could add or remove config options
- it requires documentation/translation, another hidden cost
- it bloats guix: imagine if we add configs for every 
  user-configurable app
- such configs are not easily transferrable: if I were to use the 
  same app in non-guix env, I'd have to maintain 2 configs

Another recent example is `oci-container-configuration` which 
defines a subset of docker-cli startup arguments. The problem is 
that `docker run` command has 96 options and the configuration 
only uses a handful, lacking a way to provide the remaining ones.

I think guix should not embed config generators for user software. 
The only need I see for such generators is when there are options 
which should be the same among multiple applications (e.g. color 
schemes or shared directories). For such usecase guix should 
provide better text manipulation tools which home owners could use 
to parameterise configs.

Best regards,
Sergey Trofimov