[rfc] more control over activating fallback repositories (aka what gets stacked on)

[Jonathan Lange]

On Thu, Oct 9, 2008 at 11:24 AM, Martin Pool <mbp at canonical.com> wrote:
> On Thu, Oct 9, 2008 at 10:29 AM, Robert Collins
> <robertc at robertcollins.net> wrote:
>> On Wed, 2008-10-08 at 18:21 +1300, Michael Hudson wrote:
>>> Currently, opening a branch also opens any stacked on branch specified
>>> in the branch's branch.conf file.  This is inconvenient some of the
>>> time, particularly in the innards of the codehosting system on Launchpad
>>> where we want to be able to inspect and maybe interfere with the stacked
>>> on URL before opening what it points at.
>
> At the moment we have the invariant that if you open a branch, its
> repository is always opened and configured with a fallback repository.
>  Allowing you to have a branch without those things being true will
> probably break code that expects them to be true, and I'm not sure
> it'd be generally desirable to change them to cope without it.
>
> However, we do have the shortcoming that you can't really even think
> about a branch without opening it, and you can't determine it's
> stacked on url without opening it.  One way to put this in would be to
> give the branch format the method to get the stacked-on url, and have
> the branch instance call that.
>

I have submitted a patch to Bazaar along these lines, which was
rejected for fairly sound reasons. The summary is that the
BranchConfig API needs to change before such a thing is possible.

jml