Merge branch 'sb/clone-origin'

Merge branch 'sb/clone-origin'

"git clone" learned clone.defaultremotename configuration variable
to customize what nickname to use to call the remote the repository
was cloned from.

* sb/clone-origin:
  clone: allow configurable default for `-o`/`--origin`
  clone: read new remote name from remote_name instead of option_origin
  clone: validate --origin option before use
  refs: consolidate remote name validation
  remote: add tests for add and rename with invalid names
  clone: use more conventional config/option layering
  clone: add tests for --template and some disallowed option pairs