test for non-existence of stacked on branch in mirrored area is bogus

[Michael Hudson-Doyle]

For reasons that neither of us remember, we test for the non-existence of a stacked-on branch like this:

            stacked_on_branch_url = urlutils.join(
                self.dest, stacked_on_branch_url)
            if not get_transport(stacked_on_branch_url).has('.'):
                raise StackedOnBranchNotFound()

One problem with this, which is what triggered the report, is that it doesn't handle redirects.

However, it's also bogus because the directory existing doesn't necessarily mean there's a branch there -- and in particular, for our transport as soon as you ask the question, the directory is probably created (this is a separate issue that needs fixing by itself though).

[Jonathan Lange (jml)]

The patch for this has been reviewed. Not sure if it's release-critical.

[Jonathan Lange (jml)]

Ready to land once release-critical is done.

[Jonathan Lange (jml)]

RF 7048