The format of the refspec is in the form of <source>:<destination>. For a fetch refspec, this means that <source> is the source on the remote side and <destination> is local. For a push refspec, <source> is local and <destination> is remote. The refspec can be prefixed by a + to indicate that the ref pattern can be updated even though it isn't a fast-forward update. It is not possible to use partial globs in the refspec pattern, as shown in the following line:

fetch = +refs/heads/stable*:refs/remotes/origin/stable*

However, it is possible to use namespacing. That's why we had to rewrite the stable-xxx branches to stable/xxx to fit into a namespace pattern:

fetch = +refs/heads/stable/*:refs/remotes/origin/stable/*