* lisp/org-agenda.el (org-agenda-add-time-grid-maybe): Let-bind
`org-agenda-default-appointment-duration' to nil when formatting the
grid lines. Otherwise, `org-agenda-format-item' logic fails to
produce the expected result.
* testing/lisp/test-org-agenda.el (test-org-agenda/time-grid): Add new
test set covering the bug and several simpler cases.
* testing/examples/agenda-file2.org (two): New test file example.
Reported-by: Detlef Steuer <steuer@hsu-hh.de>
Link: https://orgmode.org/list/87edv5fv1w.fsf@localhost
