Re: Would branching across repositories be theoretically possible?

On 31.12.2012 12:36, Ziemowit Laski wrote:
> My question is this: Is there a compelling technical reason why
> branching must occur within the same repository? I'm tempted to try my
> hand in adding cross-repository branching to SVN, but would like to make
> sure first that this is not impossible.

Currently it's not possible due to several constraints, for example:

  * The repository is not aware of the concept that an object it
    contains may have come from a completely different repository, and
    so does not make the repository ID part of the unique object ID.
  * Consequently, mergeinfo cannot track changes made in a foreign
    repository.

In other words, even if you could create a "branch" from a foreign repo,
you couldn't merge changes from it. At that point such a branch would be
no better than a plain code snapshot import.

Some of us discussed recently how to design this feature in a future
version, since it would be the ideal way to properly implement vendor
branches (and help bridge the barrier between different version control
systems). I can promise that it won't appear very soon, though, since it
would require serious changes to the infrastructure and assumed
invariants. Unfortunately, we've not got around to documenting our
design ideas yet.

I suppose a sort of shoehorn prototype wouldn't take that long, but
would be IMO quite disruptive if the rest of Subversion wasn't prepared
for it (maintaining backwards-compatibility being a major issue).

-- Brane

-- 
Branko Čibej
Director of Subversion | WANdisco | www.wandisco.com