New Feature: Rev Parse task should auto order arguments

[steveukx]

When using git.revparse the success of a task can be dependent on the order of arguments, eg:

git.revparse(['HEAD', '--short']) // fails
git.revparse(['--short', 'HEAD']) // succeeds

The order of arguments should be automatically set by the revparse task such that switches like --verify and --short always have the reference point after them.

At the least, a human recognisable error message should be shown rather than the git default of fatal: Needed a single revision