taskd/clone: Don't forget to use 'git config --add' for multivars setup
Neat Trick suggested by Miklos Vajna setups origin remote as '.' and
also setups 3 refspecs for remotes.origin.fetch.
The trick is nice indeed, but in order to setup config multivar, one
have to use explicit --add option for `git config' (*) or else old var
value is just replaced.
The problem showed in svn-mirror repositories with stale master (was not
updating from trunk) and also as lack of branches -- that's
understandable -- we had '+refs/remotes/tags/*:refs/tags/*' config last,
and tags were working OK.
Fix it.
(*) explicit --add was needed since
89c4afe0 (Add --add option to
git-repo-config) in git.git, which dates to git
v1.4.4.2-225-g89c4afe