Improve generated content branches

[tkw1536]

In order to improve generated content branches, we want to implement the following behaviour:

• upon client-side initialisation, we have a 'shallow clone', thus not pulling any history
• when commiting, we commit normally and send normal diffs
• when pulling, we pull normally. In case of a merge conflict, we force pull and use the server side.
• a special operation to allow squash all commits into one should exist. The plan is to use this server side when the content grows too big,