[elpa] externals/systemd fa4310a 2/4: Support for connecting to remote session bus

[Stefan Monnier]

branch: externals/systemd
commit fa4310a5f08ad1ba499d1c6ecb354035247a850b
Author: Mario Lang <mlang@delysid.org>
Commit: Mario Lang <mlang@delysid.org>

    Support for connecting to remote session bus
---
 systemd.el | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/systemd.el b/systemd.el
index 0c213ca..a7e377c 100644
--- a/systemd.el
+++ b/systemd.el
@@ -61,15 +61,32 @@
           (string (string-to-number (match-string 1 string) 16)) t t string)))
   string)
 
-(defun systemd-remote-bus (host &optional address)
-  (unless address
-    (setq address "unix:path=/run/dbus/system_bus_socket"))
+(defun systemd-remote-bus (host &optional bus)
+  "Construct a D-Bus bus address suitable for connecting to a remote D-Bus
+instance (via ssh) running on HOST.  Optional argument BUS specifies
+the D-Bus instance to connect to on the remote host.  The keywords
+:system and :session indicate to connect to the remote system or session
+bus, respectively.  If a string is given, that particular D-Bus address is used
+on the remote host.  When not specified, the remote system bus is used."
+  (setq bus
+       (pcase bus
+         ((or `nil `:system)
+          "unix:path=/run/dbus/system_bus_socket")
+         (`:session
+          (with-temp-buffer
+            (let ((default-directory (concat "/scpx:" host ":/")))
+              (shell-command "[ -e $XDG_RUNTIME_DIR/bus ] && echo -n 
$XDG_RUNTIME_DIR/bus" t)
+              (when (not (zerop (buffer-size)))
+                (buffer-string)))))
+         (_ bus)))
+  (unless bus
+    (error "Unable to determine remote session bus address."))
   (concat "unixexec:"
           "path=ssh"
           ",argv1=-xT"
           ",argv2=" (systemd-escape-dbus-address host)
           ",argv3=systemd-stdio-bridge"
-          ",argv4=" (systemd-escape-dbus-address (concat "--bus-path=" 
address))))
+          ",argv4=" (systemd-escape-dbus-address (concat "--bus-path=" bus))))
 
 (defconst systemd-dbus-service "org.freedesktop.systemd1")
 (defconst systemd-dbus-path "/org/freedesktop/systemd1")