GitLab

Set the default value when `set` encounters a PER_BUFFER variable
which has been let-bound globally, to match the behavior seen with
`make-variable-buffer-local`.

* test/src/data-tests.el (binding-test--let-buffer-local):
Add corresponding test.
(data-tests--set-default-per-buffer): Add tentative test for the
performance problem encountered in bug#41029.