The GIT repo system has been restructured to have all branches contained together inside a single repo. This allows correct change tracking and the ability to cherry pick between branches, among other pluses. The current per-branch GIT repositories will be deleted around July 20th. All git users should switch to the zimbra-foss repo before that time. The GIT wiki has been updated for the new repository:

https://wiki.zimbra.com/wiki/Building_Zimbra_using_Git

Note: It is approximately 14GB in size, so it may take some time to do the initial clone.