bug#51600: 29.0.50; Entries in ~/.mailcap are overruled (Win10)

[Arash Esbati]

Hi all,

I slightly changed the entry for "application/pdf" in my ~/.mailcap and
while trying out the result, I see that Emacs overrules my entries when
I start Gnus and write a message.  I'm on Win10 where for example I have
these 2 entries in ~/.mailcap:

    application/ms-tnef; wmopener.exe "%s"
    application/pdf;     start AcroRd32.exe %s

When I start Emacs and eval these forms in *scratch*, I get:

    (mailcap-mime-info "application/pdf")
    "start AcroRd32.exe %s"

    (mailcap-mime-info "application/ms-tnef")
    "wmopener.exe \"%s\""

As I'm writing this message, I get:

    (mailcap-mime-info "application/pdf")
    doc-view-mode

    (mailcap-mime-info "application/ms-tnef")
    nil

It used to work for me for a long time, so I suspect something went
wrong (at least for Windows) after this commit: daea9b3b44

Can others reproduce this?

Best, Arash