[Zope-dev] Mountpoints

[Tim Peters]

[Chris McDonough]
> I think I may need some remedial SVN help because I don't want to do
> this in a stupid way.  Hopefully someone will be willing to guide me
> through this.

I'll be in FB tomorrow if you'd like to pair on it (while in theory
Jim might object, I think he thinks getting this done is important
enough to offer real help -- especially if he doesn't have to offer it
himself <wink>).

> There exists a branch of the Zope 2 trunk named the zodb-blobs-branch.
> It was created as a branch of the Zope 2 trunk on September 25 (about 3
> weeks ago).

Check.

> The zodb-blobs-branch contains code that use Tim's multidatabase support
> for mountpoint support rather than the older DBTab code which
> monkeypatched ZODB and did other nasty things.  It contains a few other
> ancillary changes that make it possible to use a HEAD-ish ZODB package
> in Zope 2 as well (including changes to the setup.py I mentioned which
> allows a newer ZODB to be compiled).

Check.  Question:  does zodb-blobs-branch contain anything you _don't_
want to see on Zope trunk now?  You didn't mention anything like that
here.

> The zodb-blobs-branch happens to link in an svn external for the ZODB
> package which currently points to a *ZODB* branch named
> "blob-merge-branch".  This is really the only thing "blob-ish" about the
> zodb-blobs-branch.  All of the changes that actually cause blobs to be
> supported are isolated in that ZODB branch.  The rest of the changes are
> really just to support a later ZODB revision within Zope.  It's likely
> that this svn external can be changed to point to any 3.6-ish ZODB
> branch without breaking things too badly.

FWIW, that sounds likely to me too.

> So I'd *think* I'd like to:
>
> - create a SVN branch *from the zodb-blobs-branch* named
>  mountpoint-merge-branch

Yup.

> - change the svn external for lib/python/ZODB on the
>  mountpoint-merge-branch to point at the proper ZODB revision

Likewise.  Be sure to do an "svn up" right after (while only a bona
fide idiot could make this mistake, on two occasions so far I've
switched to a different external, run tests, and checked it in -- only
to realize later that I _hadn't_ done "svn up" so didn't actually test
anything new -- heh).

> - merge the changes that have happened since September 25 on the
>  Zope 2 trunk into the mountpoint-merge-branch

Why?  It may create headaches and I don't see the attraction.  Have
people been checking in changes to the same files over the last 3
weeks?   Even if they have, conflicts are probably easier to deal with
when the new branch gets merged back to the trunk.

> - merge the mountpoint-merge-branch back in to the trunk.

Bingo.

> But I've read the Zope SVN FAQ and it frowns on the practice of merging
> trunk changes into a branch and back again.

That's because it's so easy to lose track of what you're doing then. 
It probably can't be avoided on very long-lived branches, but this
branch is only several weeks old now, right?

> Is there a better way to do this other than applying the changes manually
> to the HEAD?

I'm not sure what this means.  As above, my natural inclination is not
to try merging anything in the trunk -> branch direction here.

> Also, what is the "right" branch of ZODB to use in the svn:external for
> lib/python/ZODB so I can test that it all works ok before I actually
> perform the merge to the HEAD?

I never leave a Zope pointing at a ZODB branch -- only at a ZODB tag. 
The only two suitable tags at this time are

    ZODB/tags/3.5.1
and
    ZODB/tags/3.6.0a4

Either should work fine for you.  If you use the latter, it may save
me some time later ;-)  But in either case, it won't last long (I'll
have to stitch in a 3.5.2 beta or 3.6.0 beta soon anyway, and tags for
those don't exist now).