Follow-up to https://git-annex.branchable.com/forum/Use_assistant_to_sync_just_git_repos__63__/#comment-88286ff5bb273eda1d731ac91197cb37

Currently, the annex.autocommit controls 3 things:

1. assistant automatically committing
2. assistant automatically syncing committs to other repos
3. sync committing when invoked

As of ff6b36c706efe1a63f121e57e45776f5f6628163 it no longer affects 2\. but that also means there's no way to control 2\. :/

The autocommit option should only configure whether the assistant automatically adds and commits new files and changes. Perhaps it should be namespaced to make its function more obvious: `annex.assistant.autocommit`

Additionally, there should be two more options to control the other two. `annex.assistant.autosync` and `annex.sync.commit` perhaps.

Making the new options namespaced would also allow the old option to retain its current function; enabling all three.

I've got multiple use-cases for git-annex where I cannot use the assistant because these finer-grained options don't exist.
