Add a documentation about GNS3 file formats

docs/file_format.rst

@@ -0,0 +1,54 @@
+GNS3 file formats
+=================
+
+The .gns3
+##########
+
+It's the topology file of GNS3 this file is a JSON with all
+the informations about what is inside the topology.
+
+A minimal version:
+
+.. code:: json
+
+    {
+        "name": "untitled",
+        "project_id": null,
+        "revision": 5,
+        "topology": {},
+        "type": "topology",
+        "version": "2.0.0"
+    }
+
+
+The revision is the version of file format:
+
+* 5: GNS3 2.0
+* 4: GNS3 1.5
+* 3: GNS3 1.4
+* 2: GNS3 1.3
+* 1: GNS3 1.0, 1.1, 1.2 (Not mentionned in the topology file)
+
+
+The .net
+#########
+It's topologies made for GNS3 0.8
+
+
+The .gns3p or .gns3project
+###########################
+
+It's a zipped version of the .gns3 and all files require for
+a topology. The images could be included inside but are optionnals.
+
+
+The .gns3a or .gns3appliance
+#############################
+
+This file contains details on how to import an appliance in GNS3.
+
+A JSON schema is available here:
+https://github.com/GNS3/gns3-registry/blob/master/schemas/appliance.json
+
+And samples here:
+https://github.com/GNS3/gns3-registry/tree/master/appliances

docs/index.rst

@@ -5,10 +5,16 @@ Welcome to API documentation!
    The API is not stable, feel free to post comments on our website
    https://gns3.com/
 
+.. WARNING::
+   This documentation are for developers for user documentation go
+   to https://gns3.com/
+
+
 .. toctree::
     general
     glossary
     development
+    file_format
 
 
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