Merge/Branch Strategy

Question

We are trying to implement the "Basic Dual Branch Plan" as described by the ALM Rangers in the latest Visual Studio TFS Branching and Merging Guide. From the guidance:

The basic branch plan with a MAIN, DEV, and RELEASE branch enables concurrent development for your next release, a stable MAIN branch for testing and a RELEASE branch for any ship blocking bug fixes. Multiple development areas are supported by creating additional development branches from MAIN. These are peers to each other and children of MAIN.

Additional releases are supported by creating release branches for each product release. Each release branch is a child of MAIN and a peer to each other (e.g. release 2.0 branch is peer to release 3.0 and both are children of MAIN). If supporting only a single release in production at a time, you may consider a single release branch, and make bug fixes directly on this branch. Once the RELEASE branch is created MAIN and the development branches can start taking changes approved for the next product release.

We are undecided as to whether we want to use a single Release branch (and label releases), or create a new release branch per release. However, there are some questions that apply either way, that don't seem to be addressed by the guidance.

My main question is: At what point in time should we create a RELEASE branch (or move tested code to the single RELEASE branch if that's the way we go)?

1. My first reaction was to create it only when ready to do the release, but then you have the problem of creating a deadlock for development and testing of the next sprint's work; you cannot check these changes into MAIN until the RELEASE branch has been created (if you do, it's more difficult to separate out the changes you only want to go to RELEASE).
2. Second idea is to create the RELEASE branch at the beginning of the sprint, and as changes pass testing in MAIN, merge them down to the current RELEASE branch. Once we reach the end of the sprint, we can lock that RELEASE branch down, and create a new one for the next sprint. This sounds like it would work, but I see no discussion of it anywhere, so I just wanted to see what people are doing.

Answer 1

I would give the same advice as Adarsh Shah in that 2 branches (MAIN, RELEASE) are sufficient in most cases, and using feature branches for things that you don't want to commit into MAIN immediately because it would take a while to be fully ready for testing. And by RELEASE I mean a branch per actual release.

Keep in mind though that, in theory, MAIN should in a release-ready state at any moment. This means using feature branches for a lot of small changes too and not merging things into MAIN as long as the feature is not considered ready. Now, this is something that you should experiment with and see what works best in your environment. If you find that it is too hard to keep MAIN into a release-ready state, by all means, create a separate DEV branch to commit the daily work. In my experience however, with some good guidelines, automated and manual testing you quickly can get into a flow where MAIN can be considered quite stable. I've worked in environments where we had a DEV branch which was highly unstable and a stable MAIN branch, and environments where we didn't have a DEV branch. Sometimes the DEV branch was needed, sometimes it became a burden to keep them in sync as both DEV and MAIN were fairly stable and essentially just a copy of each other.

Now, when should you create the release branch. It depends on the type of development you are doing. For small desktop projects or websites which have a fairly steady release cycle (a single release per sprint, for example) I find it easiest to create a release branch at the end of a sprint, and only pushing it to production the sprint after.

S1 - - S2 - - S3 - - S4 // Each sprint
     \ R1 - \ R2 - \ R3 // Release branch created at the end of a sprint
            \ P1 - \ P2 // Pushed to production at the start of the next sprint

So, at the end of S1 I create the release branch R1 from MAIN but it's not pushed to production just yet. During S2 both new features are implemented on MAIN and critical bugs are fixed on R1. If a fix on R1 is approved, it gets merged back into MAIN too, if it's required. At the end of S2, a new R2 is created, and R1 is pushed into production. I have found this approach to work quite well. You basically have a full sprint to work out the last issues in a release branch.

Of course, if a serious critical bug appears on production this bug gets priority above all else. An RXa, RXb, ... branch can then be created of the existing R-branch that's in production, implement the hot-fix and push that hot-fix into production. You can then consider whether it's needed to merge the changes from the hot-fix into your MAIN branch. Don't create a hot-fix on the MAIN branch and merge it down though, you'll find that it quickly becomes too complex because on MAIN a lot of the surrounding code might have already changed.

Answer 2

Here is what I would suggest:

1) Do all development on the Main branch until Code Complete. Code complete is the time when developers stop working on new features for that sprint but can fix regression bugs. Code complete can be few days before the release or up to a week based on how long is your sprint).

2) Create a new RELEASE branch from the MAIN at that point . Deploy the branch to QA/Staging environment to do a smoke test. After that point QA team will use RELEASE branch to do the testing for the release.

3) Developers can start working on the new features for next sprint at that point and start checking-in changes to MAIN branch. Any regression issues found during testing will be fixed in RELEASE branch first and then merged back to MAIN.

4) Any changes to code in RELEASE branch will then be pushed to QA/Staging for further testing.

5) One the Release is done any bug found in production will be fixed in RELEASE branch and hot-fixed to Prod and also merged back to MAIN.

No. 1 will be too late and no. 2 will be too early IMO.

I would suggest to create a new branch for every RELEASE and then get rid of old RELEASE branches periodically instead of using labels.

Also, I prefer having only 2 branches MAIN(which is also DEV) and RELEASE except any branch developers need to any specific feature/framework change etc. Under the root folder I usually create MAIN, RELEASES(all release branches) and BRANCHES(all branches specific to a feature/framework changes etc. but these are created only in special cases not always)