Allow overriding pathPrefix using a CLI argument

[chrispytoes]

I'm setting up a CI flow for a Gatsby site, and I'd like to be able to set the pathPrefix config value based on the environment the site is being built for. When building for development, I want to add a path prefix to host on GitLab pages, but no prefix when building for production.

Was this ever considered or is there any particular reason it hasn't been done? It seems like a no-brainer to me that this should just be a simple CLI argument like: gatsby build --prefix-paths /my-prefix.

I understand that the pathPrefix setting is ignored if --prefix-paths is not provided, but it's still a one or the other choice. I feel that the prefix is more of a choice made by the environment, and should not be embedded into a config setting in the first place.

[dasrecht]

This would be a very helpful way for folks that have setups that use different pathPrefixes for preview environments.

[dasrecht]

I found a workaround for this issue

sed -ibak "5s/blog/${PREFIX}/" gatsby-config.js

In the build pipeline i generate the needed prefix and then just before building the static preview site I replace the prefix in the gatsby-config.js

Is hacky but does its job

[violy]

you can also use environment variables, with export YOUR_PREFIX_PATH=..., dotenv and then process.env.YOUR_PREFIX_PATH inside your gatsby-config ?

[dasrecht]

Oh! I didn't even think that far. Yes that might also work and be less hacky :D Thanks a lot!