Always check for client-certificates

* lisp/net/network-stream.el
(network-stream-use-client-certificates): New user option.
(open-network-stream): If 'network-stream-use-client-certificates'
is t, and the user hasn't specified :client-certificate, do
certificate lookups via 'auth-source'.
(network-stream-certificate): Only return key and certificate
files that exist.

* doc/lispref/processes.texi (Network): Document new
client-certificate behavior.

* etc/NEWS: Document 'network-stream-use-client-certificates'.

1 files changed, 6 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 7ff9df6e0fa..b6e61c76e2f 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -322,6 +322,12 @@ Previously, this support was only available when using the external
 certificates via 'auth-source'.
 
 +++
+** New user option 'network-stream-use-client-certificates'.
+When non-nil, 'open-network-stream' performs lookups of client
+certificates using 'auth-source' as if ':client-certificate t' were
+specified.  Defaults to t.
+
++++
 ** New function 'fill-polish-nobreak-p', to be used in 'fill-nobreak-predicate'.
 It blocks line breaking after a one-letter word, also in the case when
 this word is preceded by a non-space, but non-alphanumeric character.