There is one well-known and well-tested parser which we should use,
instead of implementing parsing a second time.
The common parser is also augmented to copy the LHS into the RHS if the
latter is empty.
The expressions test had to change a bit, as we now catch a bad RHS of a
refspec locally.
We have the step-by-step method in the initialization function as we
want to remove references based on the list of references which are
already there, and we can use the convenience function for testing the
main push.
With opportunistic ref updates, git has introduced the concept of having
base refspecs *and* refspecs that are active for a particular fetch.
Let's start by letting the user override the refspecs for download.
The online::push::notes test pushes a note but leaves it hanging
around for other tests to stumble across when they're validating
that they're seeing the refs they expect to see. Clean it up on
exit.
For urls where we do not specify a username, we must handle the case
where the ssh transport asks us for the username.
Test also that switching username fails.