Previously, the name part of an repo#name url was interpreted as a
revision, similar to using the --rev option. Now it is instead looked
up as a branch first, and if that succeeds all the heads of the branch
will be processed instead of just its tip-most head. If the branch
lookup fails, it will be assumed to be an revision as before (e.g. for
tags).
In many places hg.parseurl is called with a url and "opts.get('rev')",
suggesting the second, optional argument can be None. Because opts['rev']
usually defaults to [] this never happens in practice.
However, extensions don't necessarily behave the same, but do copy this
pattern.
Also, include wider hg.parseurl tests, beyond a demonstration of the problem.
