Function tectonic_bundles::get_fallback_bundle_url

pub fn get_fallback_bundle_url(format_version: u32) -> String

Get the URL of the default bundle.

This is a mostly-hardcoded URL of a default bundle that will provide some “sensible” set of TeX support files. The higher-level tectonic crate provides a configuration mechanism to allow the user to override this setting, so you should use that if you are in a position to do so.

The URL depends on the format version supported by the engine, since that roughly corresponds to a TeXLive version, and the engine and TeXLive files are fairly closely coupled.

The URL template used in this function will be embedded in the binaries that you create, which may be used for years into the future, so it needs to be durable and reliable. We used archive.org for a while, but it had low-level reliability problems and was blocked in China. We now use a custom webservice.