Prefer settings from ~/.mailcap over system and Emacs settings

* doc/misc/emacs-mime.texi (mailcap): Document the variable and
how mailcap chooses which viewer to use.

* lisp/net/mailcap.el (mailcap-prefer-mailcap-viewers): New variable.
(mailcap-mime-info): Use it.

1 files changed, 12 insertions, 0 deletions

diff --git a/doc/misc/emacs-mime.texi b/doc/misc/emacs-mime.texi
index c0b16f30c4d..db9ed8dda76 100644
--- a/doc/misc/emacs-mime.texi
+++ b/doc/misc/emacs-mime.texi
@@ -1845,11 +1845,23 @@ Interface functions:
 @table @code
 @item mailcap-parse-mailcaps
 @findex mailcap-parse-mailcaps
+@vindex mailcap-prefer-mailcap-viewers
 Parse the @file{~/.mailcap} file.
 
 @item mailcap-mime-info
 Takes a @acronym{MIME} type as its argument and returns the matching viewer.
 
+The @code{mailcap-prefer-mailcap-viewers} variable controls which
+viewer is chosen.  The default non-@code{nil} value means that
+settings from @file{~/.mailcap} is preferred over system-wide or
+Emacs-provided viewer settings.
+
+If @code{nil}, Emacs-provided viewer settings have precedence.  Next,
+the most specific viewer has precedence over less specific settings,
+no matter if they're system-provided or private, so @string{image/gif}
+in @file{/etc/mailcap} will ``win'' over a @string{image/*} setting in
+@file{~/.mailcap}.
+
 @end table