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I see it more as the old name, I'd call the rust part bootstrap too

Yes, I would say bootstrap is the whole system of bootstrap.py + rustbuild.

The name "rustbuild" still gets used a fair bit by t-bootstrap when the distinction between the two parts is meaningful. I honestly had no idea the history of the name, I just noticed it was a term people were using that didn't seem to be written down anywhere really.

I don't think this is actually used that way? At least, I don't use rustbuild to refer to the rust part, I call that bootstrap, and disambiguate from the python part by calling the python part bootstrap.py or "the python wrapper" etc. etc.

rust-lang/rust#127434

i think having the entry is ok as a reference. i agree we should be consistent in the docs themselves, but i think a glossary entry doesn't hurt, since it will come up occasionally in old issues.

How about having this entry, but mentioning that it’s an old deprecated term?

⚠️ Warning ⚠️

• This PR is based on an upstream commit that is older than 7 days.

  It's recommended to update your branch according to the rustc-dev-guide.

Mentioned the term is deprecated.