info-xref-with-file

info-xref-with-file is a Lisp macro in `info-xref.el'.

(info-xref-with-file FILENAME &rest BODY)

Evaluate BODY in a buffer containing the contents of FILENAME.
If FILENAME is already in a buffer then that's used, otherwise a
temporary buffer.

The current implementation uses `insert-file-contents' rather
than `find-file-noselect' so as not to be held up by queries
about local variables or possible weirdness in a major mode.
`lm-with-file' does a similar thing, but it sets
`emacs-lisp-mode' which is not wanted here.