lib/repo-finder: Add Avahi based OstreeRepoFinder implementation

This is a more complex implementation of OstreeRepoFinder which resolves
ref names to remote URIs by looking for refs advertised by peers on the
local network using DNS-SD records and mDNS (Avahi). The idea is to
allow OS and app updates to be propagated over local networks, without
the internet.

It requires an OSTree server and code to generate the DNS-SD adverts in
order to be fully functional — support for this will be added
separately.

Unit tests are included.

Includes fixes by Krzesimir Nowak <krzesimir@kinvolk.io>.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

Closes: #924
Approved by: cgwalters

src/libostree/ostree-repo-finder-avahi.h

@@ -0,0 +1,62 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright © 2017 Endless Mobile, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ *
+ * Authors:
+ *  - Philip Withnall <withnall@endlessm.com>
+ */
+
+#pragma once
+
+#include <gio/gio.h>
+#include <glib.h>
+#include <glib-object.h>
+
+#include "ostree-repo-finder.h"
+#include "ostree-types.h"
+
+G_BEGIN_DECLS
+
+#define OSTREE_TYPE_REPO_FINDER_AVAHI (ostree_repo_finder_avahi_get_type ())
+
+/* Manually expanded version of the following, omitting autoptr support (for GLib < 2.44):
+_OSTREE_PUBLIC
+G_DECLARE_FINAL_TYPE (OstreeRepoFinderAvahi, ostree_repo_finder_avahi, OSTREE, REPO_FINDER_AVAHI, GObject) */
+
+_OSTREE_PUBLIC
+GType ostree_repo_finder_avahi_get_type (void);
+
+G_GNUC_BEGIN_IGNORE_DEPRECATIONS
+typedef struct _OstreeRepoFinderAvahi OstreeRepoFinderAvahi;
+typedef struct { GObjectClass parent_class; } OstreeRepoFinderAvahiClass;
+
+static inline OstreeRepoFinderAvahi *OSTREE_REPO_FINDER_AVAHI (gpointer ptr) { return G_TYPE_CHECK_INSTANCE_CAST (ptr, ostree_repo_finder_avahi_get_type (), OstreeRepoFinderAvahi); }
+static inline gboolean OSTREE_IS_REPO_FINDER_AVAHI (gpointer ptr) { return G_TYPE_CHECK_INSTANCE_TYPE (ptr, ostree_repo_finder_avahi_get_type ()); }
+G_GNUC_END_IGNORE_DEPRECATIONS
+
+_OSTREE_PUBLIC
+OstreeRepoFinderAvahi *ostree_repo_finder_avahi_new (GMainContext *context);
+
+_OSTREE_PUBLIC
+void ostree_repo_finder_avahi_start (OstreeRepoFinderAvahi  *self,
+                                     GError                **error);
+
+_OSTREE_PUBLIC
+void ostree_repo_finder_avahi_stop (OstreeRepoFinderAvahi  *self);
+
+G_END_DECLS