Updated Design: Version Control (markdown)

Design:-Version-Control.md

@@ -116,12 +116,36 @@ By default, the `localfilesystem` implementation should be entirely file based.
 
 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. 
+There are two uses to consider, that have a bearing on what configuration options
+need to be exposed.
+
+1. a user doesn't care how the repository is laid out, they just want it in a git repo
+   that allows it to be maintained externally (eg GitHub).
+
+   - User provides **flow file name**, eg `my-flows.json` - as they can today
+   - Node-RED uses a repository under `<userHome>/my-flows` - creating it if needed
+   - Node-RED stores `my-flows.json` and `my-flows_cred.json` under that directory
+
+2. a user wants to maintain a repo that contains more then just the flow files.
+
+   - User provides **git url** for an existing repo, and a **flow file name** as a
+     relative path within the repo.
+   - If it is a local repo, Node-RED uses that repo directly. A user could configure
+     a post-commit hook to handle pushing updates remotely.
+   - Otherwise, Node-RED clones that repo under `<userHome>/.flows` and uses that,
+     ensuring to do `git push` back to the origin
+   - The user should be able to provide authentication settings for the git repo
+     via settings - or by well-defined environment variables.
+
+
+
+In some environments, such as Bluemix, it isn't possible to administer a git repo
+locally outside of the Node-RED process. In this case, the user needs to be able
+to configure a git url of an existing, externally hosted, repo that should be used,
+as well as a path within the repo at that url. This needs to consider the necessary
+authentication options; for example GitHub allows you to use an application token - 
+this would need to be provided via an environment variable, rather than hardcode
+into the application.
  
 
 # Added Nodes