Merge branch 'ms/remote-usage-string'

Adds some subcommands that were not listed in "git remote --help"
usage strings.

As an independent follow-up, we may want to rethink how the overall
usage string and subcommand usage strings are maintained.

By Michael Schubert
* ms/remote-usage-string:
  remote: update builtin usage

diff --cc builtin/remote.c
Simple merge