[gnome-settings-daemon] plugins: Don't leak DESKTOP_AUTOSTART_ID into child processes

[Carlos Garnacho <carlosg src gnome org>]

commit b8f302dd93483160e05f6473845c923495a2090a
Author: Alexandr Miloslavskiy <alexandr miloslavskiy syntevo com>
Date:   Mon Mar 18 11:47:03 2019 +0100

    plugins: Don't leak DESKTOP_AUTOSTART_ID into child processes
    
    This fixes error in applications started through media-keys:
    Gtk-WARNING **: 17:48:33.761: Failed to register client: 
GDBus.Error:org.gnome.SessionManager.AlreadyRegistered: Unable to register client

 plugins/common/daemon-skeleton-gtk.h | 5 +++++
 plugins/common/daemon-skeleton.h     | 5 +++++
 2 files changed, 10 insertions(+)
---
diff --git a/plugins/common/daemon-skeleton-gtk.h b/plugins/common/daemon-skeleton-gtk.h
index b140324c..d26d6950 100644
--- a/plugins/common/daemon-skeleton-gtk.h
+++ b/plugins/common/daemon-skeleton-gtk.h
@@ -162,6 +162,11 @@ register_with_gnome_session (void)
                           NULL,
                           (GAsyncReadyCallback) on_client_registered,
                           NULL);
+
+       /* DESKTOP_AUTOSTART_ID must not leak into child processes, because
+        * it can't be reused. Child processes will not know whether this is
+        * a genuine value or erroneous already-used value. */
+       g_unsetenv ("DESKTOP_AUTOSTART_ID");
 }
 
 static void
diff --git a/plugins/common/daemon-skeleton.h b/plugins/common/daemon-skeleton.h
index 1753c2f8..7f099927 100644
--- a/plugins/common/daemon-skeleton.h
+++ b/plugins/common/daemon-skeleton.h
@@ -161,6 +161,11 @@ register_with_gnome_session (GMainLoop *loop)
                           NULL,
                           (GAsyncReadyCallback) on_client_registered,
                           loop);
+
+       /* DESKTOP_AUTOSTART_ID must not leak into child processes, because
+        * it can't be reused. Child processes will not know whether this is
+        * a genuine value or erroneous already-used value. */
+       g_unsetenv ("DESKTOP_AUTOSTART_ID");
 }
 
 static gboolean