Merge branch 'jc/doc-single-h-is-for-help' into maint

Merge branch 'jc/doc-single-h-is-for-help' into maint

Both "git ls-remote -h" and "git grep -h" give short usage help,
like any other Git subcommand, but it is not unreasonable to expect
that the former would behave the same as "git ls-remote --head"
(there is no other sensible behaviour for the latter).  The
documentation has been updated in an attempt to clarify this.

* jc/doc-single-h-is-for-help:
  Documentation: clarify that `-h` alone stands for `help`