Merge branches 'jc/clone' and 'jc/name'

Merge branches 'jc/clone' and 'jc/name'

* jc/clone:
  git-clone: typofix.
  clone: record the remote primary branch with remotes/$origin/HEAD
  revamp git-clone (take #2).
  revamp git-clone.
  fetch,parse-remote,fmt-merge-msg: refs/remotes/* support

* jc/name:
  sha1_name: make core.warnambiguousrefs the default.
  sha1_name: warning ambiguous refs.
  get_sha1_basic(): try refs/... and finally refs/remotes/$foo/HEAD
  core.warnambiguousrefs: warns when "name" is used and both "name" branch and tag exists.