Updated Design: Version Control (markdown)

Design:-Version-Control.md

@@ -66,9 +66,11 @@ Returns a promise that resolves to an array of history entries. Each entry consi
 
 ---
 
-The format of the combined flow/credential configuration is a vital detail that needs some more thinking.
+### Notes
 
-The starting point will be the already documented [new flow format](https://github.com/node-red/node-red/wiki/Design%3A-Flow-file-format-v2). With an additional `credential` property at the top level that contains the node credentials.
+ - The format of the combined flow/credential configuration is a vital detail that needs some more thinking. The starting point will be the already documented [new flow format](https://github.com/node-red/node-red/wiki/Design%3A-Flow-file-format-v2). With an additional `credential` property at the top level that contains the node credentials.
+
+ - An implementation is not required to maintain any history - it could return a single entry from the `getFlowHistory` call. This reduces the burden on implementations
 
 
 ## UI Changes
@@ -85,6 +87,43 @@ There are two parts additions to the UI:
 
 ![](images/vc-deploy-menu/vc-deploy-menu.png)
 
+
+## Implementation details
+
+
+### Local File System (default)
+
+By default, the `localfilesystem` implementation should be entirely file based.
+
+ - the base flow/credential files remain unchanged to how they work today
+ - a new directory structure is created alongside the flow file:
+
+       my-flows.json
+       my-flows_cred.json
+       .my-flows_history/
+           log.json
+           0.my-flows.json
+           0.my-flows_cred.json
+           1.my-flows.json
+           1.my-flows_cred.json
+
+   The `.<file>_history` directory contains the history of flow files; each prefixed
+   with its version id.
+
+   The `log.json` file contains the version history.
+
+### Git Repository
+
+An optional storage module will be provided that uses a Git repository for its storage.
+
+ - if the specified flow file, `my-flows.json` does not exist, it will:
+     - create an empty repository under `<userHome>/my-flows`
+     - store `my-flows.json` and `my-flows_cred.json` under that directory
+ 
+ - if the specified flow file does exist and is determined to be in a git repo, it
+   will be used as-is. 
+ 
+
 # Added Nodes
 
 Target: future
@@ -95,3 +134,5 @@ This raises some questions:
 
  - should we try to create/maintain a package.json file under the user directory - in much the same way that `npm install --save` does.
  - should we do this via the Storage API so alternative (non-filesystem) based solutions can make use of it
+
+