[gnome-software] update dialog: Show the version we are upgrading from

[Kalev Lember <klember src gnome org>]

commit 27e28360aa24ba8a0b1b7370550bbbe94f59455e
Author: Kalev Lember <klember redhat com>
Date:   Fri Jun 23 16:03:52 2017 +0200

    update dialog: Show the version we are upgrading from
    
    ... or downgrading to.
    
    https://github.com/gnome-design-team/gnome-mockups-software/blob/master/wireframes/atomic-updates.png

 src/gs-update-dialog.c |   41 ++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 40 insertions(+), 1 deletions(-)
---
diff --git a/src/gs-update-dialog.c b/src/gs-update-dialog.c
index 5fbe989..c607a6a 100644
--- a/src/gs-update-dialog.c
+++ b/src/gs-update-dialog.c
@@ -269,6 +269,39 @@ unset_focus (GtkWidget *widget)
        gtk_window_set_focus (GTK_WINDOW (widget), NULL);
 }
 
+static gchar *
+format_version_update (GsApp *app)
+{
+       const gchar *tmp;
+       const gchar *version_current = NULL;
+       const gchar *version_update = NULL;
+
+       /* current version */
+       tmp = gs_app_get_version (app);
+       if (tmp != NULL && tmp[0] != '\0')
+               version_current = tmp;
+
+       /* update version */
+       tmp = gs_app_get_update_version (app);
+       if (tmp != NULL && tmp[0] != '\0')
+               version_update = tmp;
+
+       /* have both */
+       if (version_current != NULL && version_update != NULL &&
+           g_strcmp0 (version_current, version_update) != 0) {
+               return g_strdup_printf ("%s ▶ %s",
+                                       version_current,
+                                       version_update);
+       }
+
+       /* just update */
+       if (version_update)
+               return g_strdup (version_update);
+
+       /* we have nothing, nada, zilch */
+       return NULL;
+}
+
 static GtkWidget *
 create_app_row (GsApp *app)
 {
@@ -291,7 +324,13 @@ create_app_row (GsApp *app)
        gtk_widget_set_halign (label, GTK_ALIGN_START);
        gtk_widget_set_valign (label, GTK_ALIGN_CENTER);
        gtk_box_pack_start (GTK_BOX (row), label, TRUE, TRUE, 0);
-       label = gtk_label_new (gs_app_get_update_version (app));
+       if (gs_app_get_state (app) == AS_APP_STATE_UPDATABLE ||
+           gs_app_get_state (app) == AS_APP_STATE_UPDATABLE_LIVE) {
+               g_autofree gchar *verstr = format_version_update (app);
+               label = gtk_label_new (verstr);
+       } else {
+               label = gtk_label_new (gs_app_get_version (app));
+       }
        g_object_set (label,
                      "margin-start", 0,
                      "margin-end", 20,