[geary] Add some comments to nightly flatpak-builder manifest for clarity.

[Michael Gratton <mjog src gnome org>]

commit 8df85fa781de0f4970794be0b81f5696d89637ee
Author: Michael James Gratton <mike vee net>
Date:   Tue Oct 3 15:38:26 2017 +1100

    Add some comments to nightly flatpak-builder manifest for clarity.

 org.gnome.Geary.json |   10 +++++++---
 1 files changed, 7 insertions(+), 3 deletions(-)
---
diff --git a/org.gnome.Geary.json b/org.gnome.Geary.json
index 3a832b2..447ad15 100644
--- a/org.gnome.Geary.json
+++ b/org.gnome.Geary.json
@@ -5,10 +5,13 @@
     "runtime-version": "master",
     "sdk": "org.gnome.Sdk",
     "command": "geary",
-    "tags": ["nightly"],
-    "desktop-file-name-prefix": "(Nightly) ",
     "rename-icon": "geary",
     "copy-icon": true,
+
+    /* Nightly build args, remove these when creating a new stable branch */
+    "tags": ["nightly"],
+    "desktop-file-name-prefix": "(Nightly) ",
+
     "finish-args": [
         /* X11 + XShm access */
         "--share=ipc", "--socket=x11",
@@ -102,7 +105,8 @@
             "sources": [
                 {
                     "type": "git",
-                    "url": "https://git.gnome.org/browse/geary";
+                    "url": "https://git.gnome.org/browse/geary";,
+                    "branch": "master"
                 }
             ]
         }