runner-image

This is the image that is used to build and run in pre-commit.ci.

contributing new languages

additional languages used to impact the scaling time of pre-commit.ci but are now factored in a way that they can be lazily loaded. this requires special care in the Dockerfile to make sure those languages function correctly.

a language consists of a few things after the echo: 'end minimal' marker:

• a single ENV instruction which sets up the environment variables for running that language
• a single RUN instruction which installs the language into /opt/${lang}
• the RUN instruction must also contain echo 'lang: ${lang}' such that the lazy loading machinery can identify where the language is.
• the value of ${lang} must match the language field for pre-commit.

swift is one example language that is set up in this way.