Complete README (#353)

Added some instructions for the README, also specifying how to
increase the disk size, required for the last versions.

Author: sergio-costas

README.md

@@ -1,2 +1,29 @@
-git clone -b gnome-42-2204-sdk https://github.com/ubuntu/gnome-sdk.git gnome-42-2204-sdk
+# GNOME-SDK
 
+This snap contains the SDK to build Gtk/Gnome-based snaps.
+
+## Setting disk size
+
+This snap requires quite a lot of disk space, so the default value for LXD in
+snapcraft may be not enough. To change it, just run:
+
+    lxc storage --project snapcraft device set default size=100GB
+
+This command increases the pool size for virtual disks to 100GB. Thus, the
+maximum total size for virtual disks in snapcraft will be of that size.
+
+    lxc profile --project snapcraft device set default root size=25GB
+
+This command increases the maximum disk size for each container to 25GB.
+
+## Clonning the repository
+
+There are several versions of the SDK, so a differen branch is used for each one:
+
+Core22/Gnome-42-2204:
+
+    git clone -b gnome-42-2204-sdk https://github.com/ubuntu/gnome-sdk.git gnome-42-2204-sdk
+
+Core24/Gnome-46-2404:
+
+    git clone -b gnome-46-2404-sdk https://github.com/ubuntu/gnome-sdk.git gnome-46-2404-sdk