In version control, we have a main branch and recently created a release branch. We were dicussing, where to fix an issue and where to merge it (fix in main and forward integrate to release or fix in release and reverse integrate to main).
Microsoft states in their "Branching and Merging Primer" (https://learn.microsoft.com/de-de/vsts/repos/tfvc/branching-strategies-with-tfvc?view=vsts) that one should never forward integrate from main to release. But they don't present I reason, nor can I think of one.
Is there a reason for this?
A lot depends on your particular way to use a SCM - independently of which one you use.
It makes a difference if you are a company with 1000 committers working on one single
product or if you are talking about a tiny project with just 3 people.
However in general it is indeed not a good idea to merge changes from a main line to
a release line.
Imagine your mainline frequently gets commits (either directly or merged from other branches).
Now we assume that the main branch got some bugfixes that you also want in your release branch.
If you attempt to merge the bugfixes from main to release you probably run into problems, because the bugfixes are entangled with other changes that you don't want in your release branch (possibly because they implement new features for the next release).
Also the merging process might result in new mistakes/errors and break the release which you probably do not want.
See:
This also depends on the question if you want to alter an existing release at all.
You could instead create a new release based on the previous one and then merge
the desired changes from main and subsequently fix them.
This is more or less the same, but with the difference that you never touch an existing release (which may be of importance for you or may be not).
See:
A clean way to update the existing release would be to branch off a temporary branch
from your release branch, then merge the relevant changes from main. After subsequently fixing the temporary branch you can merge it to the release which should now be a simple copy operation without the risk of breaking anything.
See:
Update:
After reading your question again I found that you're thinking about changing in the release and then merging to main.
IMHO a release branch should never ever be used for developing any changes. It should always only pick up changes that were developed and tested in other branches. After all the reason of having release branches is that they are stable and reliable. Any development ruins that.
Related
We're working by the git-flow workflow. Typically we release some release candidates (RC, v1.0.0-rc.0) before we ship the final release (v1.0.0).
To do so, we have a release branch (release/1.0.0). The release candidates are just tags within that branch. The release branch is not merged into main until we have a final release.
Today we discussed whether we should open a release branch for every release candidate (e.g. `release/1.0.0-rc.0) and merge these into main whenever the candidate is released.
Any opinions on this one?
Generally, if each of the previous release candidates are reachable by the newest one, then they could be on the same branch, and therefore there isn't any benefit to having separate branches for each.
If you wish to make a new release candidate that does not start from the current release candidate (e.g. perhaps you need to back up a few commits, or even start over), then that would be a good time to consider creating a new branch.
I assume once you merge into main you can delete all of the release branches, whether they were fully merged into main or not. Since you still have the old release versions tagged that you didn't use, you could always go back to them if you wish, even without the branches.
Update: We ended up using a process very much like this schema (thanks to neuro for the link). We massaged out repository into a state where default is stable (and has the same code as our production environment), we have a dev branch, feature branches for new stuff and use release branches for releases. All seems to be working perfectly.
Backstory
Our team has recently switched from using SVN (using ToroiseSVN Windows client) to Mercurial (using TortoiseHg Windows client) for version control. We have successfully exported our SVN repository and imported it into a Mercurial repository.
We now have a Mercurial repository where we can see the entire history of revisions (changesets in Mercurial).
How we did it in the old days
Life was simpler in the old days; our development process was not really multi-stream like it is now. The trunk was used to hold all code - even changes that were still in-flight (as long as it didn't break the trunk). When it came to managing releases with SVN, we would checkout the trunk (which holds all code), revert the individual changes we didn't want as part of the release, and create a tag for it.
Cherrypicking the code we want with SVN was easy. Bug-fixing previous releases and ensuring it was part of the trunk was simple too.
What we are doing now
In Mercurial, we need to be able to get a snapshot of the "trunk" (default in Mercurial) with individual changes reverted out. We can do this using hg revert.
To snapshot this, we have created a "named branch" - let's call it Build-4.0.1 for now.
Where the challenge arises
Development continues on default as normal when a bug is found in Build-4.0.1. Let's assume the bug is in one of the reverted files. We change the code from the branch for Build-4.0.1, create a new "named branch" (Build-4.0.2) and want to merge it back into default without pushing the reverted code over the top of newer code. How can we accomplish this?
Alternatively, is there a better workflow for managing the releases and our code in Mercurial? I quite like the look of this wonderful SO answer on managing release branches, although I am not sure how we can transition to it from the state we are in now (with in-flight stuff in default).
Note: I have looked at the Transplant extension, but haven't used it yet - could it be part of the solution to this challenge?
Well, to begin with, your use of revert seems strange to me. Usually it is used to revert modifications done to the working copy back to the version of the repository.
The usual way to get the working copy to some point backward is to update :
hg update -r 1234
from there, you can tag, modify, commit, etc.
To merge back you only have to merge your release branch to the default branch. It will work like a charm, unless it is to different/old a release.
Transplant works fine, but do something a bit different from merge : it take your changeset as a "diff" and apply it as a new modification.
To manage your releases, you can look this other answer (by me) :
How to use mercurial for release management?
What we use is a clone / main branch that holds the most stable version, which is released at some points. On this clone : branch, we can fix critical bugs (hotfix). In parallel, we use a dev clone / branch to develop. The hotfixes are merge as soon as completed from stable to dev. When the current development is done, we merge the dev on stable / default.
This schema is pretty good to understand things :)
Good luck !
Going through all the changes and taking out the ones you don't want is not a common way of creating a release, to put it mildly. The Common Branching Patterns section in the SVN book suggest some more popular work flows:
release branches: create release branch from unstable trunk, fix bugs to stabilize it, cherry pick bug fixes between them while the branch is in maintenance mode.
feature branches: keep the trunk stable and ready for release by only merging in the feature branches that you want
The second one is probably the best fit here, because it gives you a place to put experimental or risky changes until you feel confident about them - these are the changes you would have reverted before a release in your old workflow.
Both of these branching patterns should carry over just fine to mercurial. In case you go for the first approach, note that mercurial (since 2.0) now has a graft command, you no longer need the transplant extension.
We have team of 10 developers who works parallel for different features, sometimes these features use common code sometime no.
And now we're changing our process to branch-per-feature and it seems mercurial is more suitable for such development.
I see this process so:
1. make release branch (r-b) from default(trunk)
2. make feature branch (f-b) from default(trunk)
When developer thinks his feature is done he can merge f-b to r-b. When it's time to go to QA we merge all finished f-b to r-b and create release for our QAs.
Questions:
When QA finds a bug developer should modify his f-b and merge it again to r-b. Does it mean that developer just switch to his f-b and start fixing the bug and then makes simple merge f-b to r-b again?
When release is passed QA it goes to PROD - how can we freeze changes? "hg tag" is good choice but someone can update tag if he really wants it.
Thanks
If you're going to merging into specific release branches then your feature branches should be branched from the release branch, not the trunk. It is simpler to merge with the parent branch than a non-parent branch.
1) If you really want to do feature branches then each bug would have its own branch. This will help keep bug fixes separate from new features. After all, it's branch-per-feature not branch-per-developer.
2) Hg tag is what I have used. You are right that someone change move a tag if they really want to, but tags are versioned and you can install hooks on the main hg repo to throw alerts if a tag is moved. I really wouldn't worry about tags being moved unless you can't trust your developers, in which case you are screwed.
The answer to your first question is 'yes'.
The best way to freeze for release is to have a separate release clone that only the release manager can push/pull changesets to. Just because you're using branches doesn't mean multiple-clones don't have a place in your workflow. Have a clone that QA does final pre-flight testing on to which developers can't push changes makes for a great firewall.
Also, consider using bookmarks for your feature branches. Since, as I'm sure you know, Mercurial named branch names never go away the git-like bookmarks work well for sort lived concepts like features and bugs.
I have been tasked with coming up with a strategy for branching, merging and releasing over the next 6 months.
The complication comes from the fact the we will be running multiple projects all with different code changes and different release dates but approximately the same development start dates.
At present we are using VSS for code management, but are aware that it will probably cause some issues and will be migrating to TFS before new development starts.
What strategies should I be employing and what things should I be considering before setting a plan down?
Sorry if this is vague, feel free to ask questions and I will update with more information if required.
This is the single best source control pattern that I have come across. It emphasizes the importance of leaving the trunk free of any junk (no junk in the trunk). Development should be done in development branches, and regular merges (after the code has been tested) should be made back into the trunk (Pic 1), but the model also allows for source to be patched while still under development (Pic 2). I definitely recommend reading the post in its entirety, to completely understand.
Pic 1
Pic 2
Edit: The pictures are definitely confusing without words. I could explain, but I would basically be copying the original author. Having said that, I probably should have selected a better picture to describe the merge process, so hopefully this helps. I'd still recommend reading the post, however:
The simplest and most usual way I've seen branching work is off two premises. Trunk and Release. I think this is known as the "Unstable trunk, stable branch" philosophy.
Trunk is your main source. This contains the "latest and the greatest" code and is forward looking. It generally isn't always stable.
Release is a one-to-many association with trunk. There is one trunk but many releases that derive from the trunk. Releases generally start with a branch of the trunk once a particular functionality milestone has been hit so the "only" things left to go in for a particular deployment should just be bug fixes. You then branch the trunk, give it a label (e.g. 1.6 Release is our current latest Release), build and send the release to QA. We also push the version number (usually the minor number) of the trunk up at this point to ensure we don't have two releases with the same number.
Then you begin the testing cycle on your release branch. When sufficient testing has been perfomed you apply bug fixes to the release branch, merge these back to the trunk (to ensure bug fixes are carried forward!) and then re-release a build of the branch. This cycle with QA continues until you are both happy and the release is finally given to the customer(s). Any bug reports from the customer(s) that are accurate (i.e. they are a bug!) start another QA cycle with the branch in question.
As you create future releases it is a good idea to also try to move older customers onto newer branches to reduce the potential number of branches you might have to back-patch a bug fix into.
Using this technique you can deploy solutions using your technology to a variety of customers that require different levels of service (starting with least first), you can isolate your existing deployments from "dangerous" new code in the trunk and the worst merge scenario is one branch.
My first recommendation would be to read Eric Sink's Source Control HOWTO - specifically the branches and branch merge chapters.
We have 3 containers - DEV, MAIN, and RELEASE for our work. MAIN contains all our "ready-to-release" code and we tend to think of it as "basically stable." DEV/Iteration (or DEV/Feature, or DEV/RiskyFeatureThatMightBreakSomeoneElse) are branches from MAIN and are merged up when the Iteration/Feature is ready to promote up past the DEV environment. We also have TFS builds set up from the DEV/Iteration branch and the MAIN branch.
Our RELEASE container contains numbered releases (similar to the "tags" container used in many Subversion repositories). We simply take a branch from MAIN each time - I like to say we're "cutting" a RELEASE branch to signify this shouldn't have a lot of activity going on once the merge is finished.
As for VSS->TFS - Microsoft supports an upgrade path which should keep your version history, but if you don't need it the history, I would just get the latest version from VSS, check it into TFS and archive the VSS repository.
One final tip - get your team members familiar with source control. They must understand branching and merging or you will be stuck doing a lot of cleanup work :).
Good luck!
The subversion book describes some common branching patterns. Maybe you can also apply these to TFS.
this may be a naive question, but, as asked in the object, what is the actual way used by versioning softwares to merge a branch back into the main trunk without generating broken code?
Here's a quick example: I make a branch out of the main trunk for the program "Hello World Power edition". I add support for Klingon. This is a radical change that changes the way the function printHelloWorld() works.
Meanwhile, because of bug #749 that cause "Hello World" to be written "Helo World", the function printHelloWorld() in the main trunk has been changed.
Now, the problem that I see here is: when i merge by branch back to the main trunk i experiment a clash in the function printHelloWorld() within the file sayHello.py
How does a VCS program know how to add the Klingon support from my branch and keep the bug fix in the main trunk? What are the human-driven or software-driven strategies to avoid this?
Thanks in advance.
How does a VCS program know how to add
the Klingon support from my branch and
keep the bug fix in the main trunk?
VCS knows nothing about semantic of your source code it sees it as a bunch of text/binary files. VCS system uses diff / merge algorithms to detect conflicts between yours and current file version. It is your responsibility to resolve such conflicts because only you know semantic of these changes. Some VCSs like SVN would require you to update your working copy with latest changes from trunk before allowing you to commit changes to make sure that nothing is lost.
To make sure that you didn't break anything and all previous bug fixes were not broken you should use code reviews, unit tests and other practices. Continuous integration is a good way to keep software healthy.
In such a case the version control system can't merge automatically, you have to do the merge by hand. Good unit tests will help you to ensure that no functionality is lost.
Before you can merge your branch back to trunk, the version control system will update your working copy with the changes in trunk since you branched out. It will just not allow you to merge without this update. This ensures you get all the bug fixes in the trunk in your next commit.
A good strategy for working on a branch is to port changes in trunk into you branch on very regular basis. This ensures that you don't drift too apart from trunk, leading you to have problems when you eventually merge back into trunk.