[gimp] Issue #8520: show devel download link when relevant.

[Jehan <jehanp src gnome org>]

commit 08b7de3b137216788f43224bffac19ba0ee2efe8
Author: Jehan <jehan girinstud io>
Date:   Wed Aug 31 13:13:27 2022 +0200

    Issue #8520: show devel download link when relevant.
    
    This is shown in the About dialog when a new version is available, but
    also in the debug dialog (also when a new version is available).
    
    Of course, for stable versions, we should still show the main download
    page (which I double-checked current code does).

 app/dialogs/about-dialog.c       | 10 ++++++++--
 app/widgets/gimpcriticaldialog.c |  4 ++++
 2 files changed, 12 insertions(+), 2 deletions(-)
---
diff --git a/app/dialogs/about-dialog.c b/app/dialogs/about-dialog.c
index c5d7eec93f..9f061ff860 100644
--- a/app/dialogs/about-dialog.c
+++ b/app/dialogs/about-dialog.c
@@ -332,7 +332,8 @@ about_dialog_add_update (GimpAboutDialog *dialog,
   if (config->last_known_release != NULL)
     {
       /* There is a newer version. */
-      gchar *comment = NULL;
+      const gchar *download_url = NULL;
+      gchar       *comment      = NULL;
 
       /* We want the frame to stand out. */
       label = gtk_label_new (NULL);
@@ -350,9 +351,14 @@ about_dialog_add_update (GimpAboutDialog *dialog,
       gtk_image_set_from_icon_name (GTK_IMAGE (button_image),
                                     "software-update-available",
                                     GTK_ICON_SIZE_DIALOG);
+#ifdef GIMP_UNSTABLE
+      download_url = "https://www.gimp.org/downloads/devel/";;
+#else
+      download_url = "https://www.gimp.org/downloads/";;
+#endif
       g_signal_connect (button, "clicked",
                         (GCallback) about_dialog_download_clicked,
-                        "https://www.gimp.org/downloads/";);
+                        (gpointer) download_url);
 
       /* The preferred localized date representation without the time. */
       datetime = g_date_time_new_from_unix_local (config->last_release_timestamp);
diff --git a/app/widgets/gimpcriticaldialog.c b/app/widgets/gimpcriticaldialog.c
index 443f2e0ee4..2c7d5b1ea6 100644
--- a/app/widgets/gimpcriticaldialog.c
+++ b/app/widgets/gimpcriticaldialog.c
@@ -445,7 +445,11 @@ gimp_critical_dialog_response (GtkDialog *dialog,
       break;
 
     case GIMP_CRITICAL_RESPONSE_DOWNLOAD:
+#ifdef GIMP_UNSTABLE
+      url = "https://www.gimp.org/downloads/devel/";;
+#else
       url = "https://www.gimp.org/downloads/";;
+#endif
     case GIMP_CRITICAL_RESPONSE_URL:
       if (url == NULL)
         {