Merge branch 'nd/completion-negation'

Merge branch 'nd/completion-negation'

Continuing with the idea to programmatically enumerate various
pieces of data required for command line completion, the codebase
has been taught to enumerate options prefixed with "--no-" to
negate them.

* nd/completion-negation:
  completion: collapse extra --no-.. options
  completion: suppress some -no- options
  parse-options: option to let --git-completion-helper show negative form