Patch Set 2: I would prefer that you didn't submit this

Looks good, but I think the set of operations which should be disabled when there is no commit yet is incomplete. I think the following operations should be also disabled:

Team menu:
- Synchronize
- Pull (if no upstream configuration is available)

Repositories View:
- Merge
- Rebase
- Import Projects
- Create Branch (on Branches node)
- Push to Upstream (there is nothing to push yet)
- Push...

In addition we should show some hint on the label decorators otherwise it's hard to understand why all these menus are disabled:

[jgit|Empty master]