Fix bug that erases org buffer when calling agenda via org-agenda-open-link.
[My apologies, but I'm afraid my first attempt at this patch mistook a
necessary second check for redundancy. Here is an improved version.]
* lisp/org-agenda.el (org-prepare-agenda): If the agenda is called
from within the agenda via an elisp link, such as
[[elisp:(org-agenda-list)]], org-prepare-agenda erases the buffer of
the file containing the link, since that buffer is current during
org-prepare agenda (due to a with-current-buffer in
org-agenda-open-link). An additional test now ensures that the
agenda buffer is in fact current when the buffer is erased and local
variables for the agenda are set.