This one should be easy to debug since
(org-export-file-uri "/address@hidden:papers/last.pdf")
is easy to reproduce. Could you investigate where the spurious "/" comes
from?
This seems to be related to a tramp file notation change on emacs master. I don't use tramp, but I heard about it on emacs-devel.
Here is a test _expression_:
(find-file-name-handler "/address@hidden:papers/last.pdf" 'file-remote-p)
On emacs 25.2, that returns tramp-file-name-handler.
On emacs master, that returns nil.
So, on emacs 25.2, in org-export-file-uri, the (org-file-remote-p filename) case evaluates to true. Whereas, on emacs master, the execution falls into the default (t ..) case.
.. and thus the spurious "/".
Copying the tramp dev Michael Albinus on this for help.
@Michael How should the above find-file-name-handler arg change to support that test file path?
Thanks.