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RE: Branching/Merging Strategy

From: Varnau, Steve (Seaquest R&D) <steve.varnau_at_hp.com>
Date: Mon, 20 Feb 2012 17:39:41 +0000

> -----Original Message-----
> From: John Maher [mailto:JohnM_at_rotair.com]
> Sent: Monday, February 20, 2012 5:37 AM
> To: Varnau, Steve (Seaquest R&D)
> Subject: RE: Branching/Merging Strategy
> Hello
> I'm new to subversion and have two questions.
> 1) How do I properly make a post? I get these e-mails but no where do
> I see any information on how to put a post up.

Just mail to users_at_subversion.apache.org. I've copied the list on this response.

> 2) I had a problem with a merge where code from one function had gotten
> placed in another along with all kinds of other problems to the point
> where I do not feel comfortable with the merge. It took a week going
> through backups to fix the code. I would like to learn how to use it
> without problems but something in the statement confused me. The
> statement "A common pattern is that the trunk is for new feature
> development" doesn't make much difference between using the trunk for
> production and branches for future releases if the trunk and branch are
> just labels that have no meaning. Or is there some hidden meaning that
> I do not know about?

The naming does not really matter. In my project, what we treat as our trunk is not really named "trunk". But that is the common terminology used in the list.

The pattern of usage is the key thing, not the names. So one place where all the changes get integrated back together into a common source tree is the logical trunk, whether we call it trunk, branch/main, or bob.

The original poster is using a pattern where the trunk is what is in "production". So when a feature is ready to go into production, they merge it in. I am suggesting that a more common method is the reverse -- when something is ready for production, branch it off.

For instance, the subversion software itself has to support old releases that are in the field, not just one "production" version. So, features are developed on the trunk and when getting ready to release, they create a release branch. Fixes can be made on those branches, released, and also merged back to trunk for future releases. But the trunk is never synched (merged) back to those release branches.

So in this model, there is a main line of development (trunk), and two kinds of side branches. Release branches and development branches. As I described above, release branches are not synched up to the trunk, but development branches are synched before they are reintegrated.

Nothing magic in the naming, and subversion does not keep track of which branches are what types. It is just in the merging patterns used. You are left to keep track of that by naming schemes, etc.

> Thanks
> Mar

Hope that helps.

> -----Original Message-----
> From: Varnau, Steve (Seaquest R&D) [mailto:steve.varnau_at_hp.com]
> Sent: Sunday, February 19, 2012 1:34 PM
> To: leojhartiv; users_at_subversion.apache.org
> Subject: RE: Branching/Merging Strategy
> > From: leojhartiv [mailto:leo.hart_at_gmail.com]
> > Sent: Saturday, February 18, 2012 8:36 AM
> > To: users_at_subversion.apache.org
> > Subject: Branching/Merging Strategy
> >
> > I wanted to describe our branching and merging strategy and hopefully
> get some feedback. We are using Subversion Server 1.6.
> >
> > Currently we manage trunk plus up to 3 other branches:
> > * trunk: always represents "what's in production"
> > * 1.0.0, 2.0.0, etc: represent long-term (normally quarterly)
> development branches
> > * 1.1.0, 1.2.0, etc: represent monthly maintenance branches
> > * 1.0.1, 1.0.2, etc: represent "deploy immediately" hot fix branches
> > Our process of creating a branch is to svn copy from trunk into the
> new branch. So in the case of a new development branch:
> > svn copy "http://myrepos/trunk" "http://myrepos/branches/2.0.0"
> > Or in the case of a new maintenance branch:
> > svn copy "http://myrepos/trunk" "http://myrepos/branches/1.1.0"
> > When either branch has been deployed to production, we use a svn merge
> reintegrate to merge it back into trunk. So in the case of the
> maintenance branch:
> > svn --accept p merge --reintegrate "http://myrepos/branches/1.1.0"
> "http://myrepos/trunk"
> > We then merge trunk into any future releases still pending and resolve
> any conflicts:
> > svn merge "http://myrepos/trunk" "http://myrepos/branches/2.0.0"
> > This has worked well in most instances. The reintegrate option almost
> never has any conflicts. However, when we got close to deploying 2.0.0
> we ran into trouble.
> > 1 or 2 weeks before we were ready to launch 2.0.0, some of the team
> needed to start work on 2.1.0 and 3.0.0 while others were finishing up
> on 2.0.0. The normal process would be to create 2 branches off trunk:
> > svn copy "http://myrepos/trunk" "http://myrepos/branches/2.1.0"
> > svn copy "http://myrepos/trunk" "http://myrepos/branches/3.0.0"
> > Unfortunately, this won't really work as much of the work on these
> branches depends on completed work currently in 2.0.0, but not yet
> merged to trunk (since we haven't gone to production yet).
> > So what we did was create these branches off of 2.0.0:
> > svn copy "http://myrepos/branches/2.0.0"
> "http://myrepos/branches/2.1.0"
> > svn copy "http://myrepos/branches/2.0.0"
> "http://myrepos/branches/3.0.0"
> > This worked fine until we started reintegrating 2.0.0 back into trunk
> and out to 2.1.0 and 3.0.0. We've found that all of our merges are
> missing change-sets and often report conflicts that don't really exist.
> My guess is that branching off of 2.0.0 has confused subversion's
> automatic merge tracking, but I honestly don't understand how all of
> that works enough to be sure.
> >
> > My questions are:
> > * How are other teams handling the above scenario?
> > * Is there a different approach we should be using?
> > Thanks for your help!
> The merge problems you describe (synching trunk to 2.1.0) can be done
> correctly, but they are harder to get correct. You need someone who
> really understands branching and 2-URL merging. I often have to draw the
> branches on a whiteboard and identify the ranges/deltas that need to be
> merged.
> That being said, your branch strategy may be making it harder than it
> needs to be. Many times multiple versions of software may be in
> production or supported at a time, rather than a single version in
> production. A common pattern is that the trunk is for new feature
> development, and then released software is branched off. Any
> fixes/patches go on the side branch and also merged back to trunk for
> future releases.
> -Steve
Received on 2012-02-20 18:40:49 CET

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