Best Branching and Merging strategies in Gerrit

Best Branching and Merging strategies in Gerrit

Step 1 – First Lets read this article about Best Branching and Merging strategies in git

Best Branching and Merging strategies in git

Step 2 – Now Lets learn the Gerrit Merge Types

Step 3 – Time to Learn the Types of Submit in Gerrit

Step 4 – Finally, You must read the recommendations below

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Best Branching and Merging strategies in git

Best Branching and Merging strategies in git

Step 1 – First you need to learn the needs of branches. This is very good read.


Step 2 – Now time has come to Learn best branching model in Git.


Step 3 – Now, Lets understand, what is the kind of merges we have in Git?


Step 4 – Are you still having a questions, Please post in the comment section.

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Important Configuration Definitions

  • Source code— Files written in high-level languages such as C# that need to be compiled (for example, foo.cs).
  • Source(s)— All the files involved in building a product (for example, C, CPP, VB, DOC, HTM, H, and CS). This term is used mostly as a catch-all phrase that is specific not only to source code files but to all the files that are stored in version tracking systems.
  • Codeline— A tree or branch of code that has a specific purpose, such as the mainline, release line, or hotfix line that grows collectively.
  • Mainline or trunk (“The Golden Tree”)— The main codeline of the product that contains the entire source code, document files, and anything else necessary to build and release the complete product.
  • Snapshot— A specific point in time in which the sources and build are captured and stored, usually on a release or build machine.
  • Milestone— A measurement of work items that includes a specified number of deliverables for a given project scheduled for a specified amount of time that are delivered, reviewed, and fixed to meet a high quality bar. The purpose of a milestone is to understand what is done, what is left to do, and how that fits with the given schedule and resources. To do this, the team must complete a portion of the project and review it to understand where the project is in the schedule and to reconcile what is not done with the rest of the schedule. A milestone is the best way to know how much time a portion of the project will take.
  • Code freeze— A period when the automatic updates and build processes are stopped to take the final check-ins at a milestone.
  • Public build— A build using the sources from the mainline or trunk.
  • Private build (also referred to as a sandbox build)— A build using a project component tree to build more specific pieces of the product. This is usually done prior to checking in the code to the mainline.
  • Branching— A superset of files off the mainline taken at a certain time (snapshot) that contains new developments for hotfixes or new versions. Each branch continues to grow independently or dependently on the mainline.
  • Forking— Cloning a source tree to allow controlled changes on one tree while allowing the other tree to grow at its own rate. The difference between forking and branching is that forking involves two trees, whereas branching involves just one. It is also important to note that forking or cloning makes a copy (snapshot) of the tree and does not share the history between the two trees, whereas branching does share the history.
  • Virtual Build Labs (VBLs)— A Virtual Build Lab is a build lab that is owned by a specific component or project team. The owner is responsible for propagating and integrating his code into the mainline or public build. Each VBL performs full builds and installable releases from the code in its source lines and the mainline. Although the term virtual is used in the name of the labs, don’t confuse it with Virtual PC or Virtual Machines because the labs are real physical rooms and computer boxes. It is not recommended that you use Virtual software for build machines except possibly for an occasional one-off or hotfix build. , “The Build Lab and Personnel.” There is usually a hierarchy of VBLs so that code “rolls up” to the mainline or trunk. For example, let’s say that you have a mainline, Project A is a branch off of the mainline, and Developer 1 has a branch off the project branch. Developer 1 has several branches off his branch, with each branch representing a different component of the product. If he wants to integrate one of his branches into main, he should first merge his changes with all the levels above the branch to make sure he gets all the changes. Alternatively, he can just roll the changes into main, which sits higher in the hierarchy. This will become clearer in the next couple of pages.
  • Reverse integration (RI)— The process of moving sources from one branch or tree to another that is higher in the VBL hierarchy.
  • Forward integration (FI)— The process of moving sources from one branch or tree to another that is lower in the VBL hierarchy.
  • Buddy build— A build performed on a machine other than the machine that the developer originally made changes on. This is done to validate the list of changed files so that there are no unintended consequences to the change in the mainline build.
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GIT Tutorial – Branching and Merging


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A Successful Git branching model | Git branching model Guide


I was reading article and thought to repost here.

It focuses around Git as the tool for the versioning of all of our source code.

Why git?

For a thorough discussion on the pros and cons of Git compared to centralized source code control systems, see the web. There are plenty of flame wars going on there. As a developer, I prefer Git above all other tools around today. Git really changed the way developers think of merging and branching. From the classic CVS/Subversion world I came from, merging/branching has always been considered a bit scary (“beware of merge conflicts, they bite you!”) and something you only do every once in a while.

But with Git, these actions are extremely cheap and simple, and they are considered one of the core parts of your daily workflow, really. For example, in CVS/Subversion books, branching and merging is first discussed in the later chapters (for advanced users), while in every Git book, it’s already covered in chapter 3 (basics).

As a consequence of its simplicity and repetitive nature, branching and merging are no longer something to be afraid of. Version control tools are supposed to assist in branching/merging more than anything else.

Enough about the tools, let’s head onto the development model. The model that I’m going to present here is essentially no more than a set of procedures that every team member has to follow in order to come to a managed software development process.

Decentralized but centralized

The repository setup that we use and that works well with this branching model, is that with a central “truth” repo. Note that this repo is only considered to be the central one (since Git is a DVCS, there is no such thing as a central repo at a technical level). We will refer to this repo as origin, since this name is familiar to all Git users.

Each developer pulls and pushes to origin. But besides the centralized push-pull relationships, each developer may also pull changes from other peers to form sub teams. For example, this might be useful to work together with two or more developers on a big new feature, before pushing the work in progress to origin prematurely. In the figure above, there are subteams of Alice and Bob, Alice and David, and Clair and David.

Technically, this means nothing more than that Alice has defined a Git remote, named bob, pointing to Bob’s repository, and vice versa.

The main branches

At the core, the development model is greatly inspired by existing models out there. The central repo holds two main branches with an infinite lifetime:

  • master
  • develop

The master branch at origin should be familiar to every Git user. Parallel to the master branch, another branch exists called develop.

We consider origin/master to be the main branch where the source code of HEAD always reflects aproduction-ready state.

We consider origin/develop to be the main branch where the source code of HEAD always reflects a state with the latest delivered development changes for the next release. Some would call this the “integration branch”. This is where any automatic nightly builds are built from.

When the source code in the develop branch reaches a stable point and is ready to be released, all of the changes should be merged back into master somehow and then tagged with a release number. How this is done in detail will be discussed further on.

Therefore, each time when changes are merged back into master, this is a new production release by definition. We tend to be very strict at this, so that theoretically, we could use a Git hook script to automatically build and roll-out our software to our production servers everytime there was a commit on master.

Supporting branches

Next to the main branches master and develop, our development model uses a variety of supporting branches to aid parallel development between team members, ease tracking of features, prepare for production releases and to assist in quickly fixing live production problems. Unlike the main branches, these branches always have a limited life time, since they will be removed eventually.

The different types of branches we may use are:

  • Feature branches
  • Release branches
  • Hotfix branches

Each of these branches have a specific purpose and are bound to strict rules as to which branches may be their originating branch and which branches must be their merge targets. We will walk through them in a minute.

By no means are these branches “special” from a technical perspective. The branch types are categorized by how we use them. They are of course plain old Git branches.

Feature branches

May branch off from: develop
Must merge back into: develop
Branch naming convention: anything except masterdevelop,release-*, or hotfix-*

Feature branches (or sometimes called topic branches) are used to develop new features for the upcoming or a distant future release. When starting development of a feature, the target release in which this feature will be incorporated may well be unknown at that point. The essence of a feature branch is that it exists as long as the feature is in development, but will eventually be merged back into develop(to definitely add the new feature to the upcoming release) or discarded (in case of a disappointing experiment).

Feature branches typically exist in developer repos only, not inorigin.

Creating a feature branch

When starting work on a new feature, branch off from the develop branch.

$ git checkout -b myfeature develop Switched to a new branch "myfeature"

Incorporating a finished feature on develop

Finished features may be merged into the develop branch definitely add them to the upcoming release:

$ git checkout develop Switched to branch 'develop' $ git merge --no-ff myfeature Updating ea1b82a..05e9557 (Summary of changes) $ git branch -d myfeature Deleted branch myfeature (was 05e9557). $ git push origin develop

The --no-ff flag causes the merge to always create a new commit object, even if the merge could be performed with a fast-forward. This avoids losing information about the historical existence of a feature branch and groups together all commits that together added the feature. Compare:

In the latter case, it is impossible to see from the Git history which of the commit objects together have implemented a feature—you would have to manually read all the log messages. Reverting a whole feature (i.e. a group of commits), is a true headache in the latter situation, whereas it is easily done if the --no-ff flag was used.

Yes, it will create a few more (empty) commit objects, but the gain is much bigger that that cost.

Unfortunately, I have not found a way to make --no-ff the default behaviour of git mergeyet, but it really should be.

Release branches

May branch off from: develop
Must merge back into: develop and master
Branch naming convention: release-*

Release branches support preparation of a new production release. They allow for last-minute dotting of i’s and crossing t’s. Furthermore, they allow for minor bug fixes and preparing meta-data for a release (version number, build dates, etc.). By doing all of this work on a release branch, the develop branch is cleared to receive features for the next big release.

The key moment to branch off a new release branch from develop is when develop (almost) reflects the desired state of the new release. At least all features that are targeted for the release-to-be-built must be merged in to develop at this point in time. All features targeted at future releases may not—they must wait until after the release branch is branched off.

It is exactly at the start of a release branch that the upcoming release gets assigned a version number—not any earlier. Up until that moment, the develop branch reflected changes for the “next release”, but it is unclear whether that “next release” will eventually become 0.3 or 1.0, until the release branch is started. That decision is made on the start of the release branch and is carried out by the project’s rules on version number bumping.

Creating a release branch

Release branches are created from the develop branch. For example, say version 1.1.5 is the current production release and we have a big release coming up. The state of develop is ready for the “next release” and we have decided that this will become version 1.2 (rather than 1.1.6 or 2.0). So we branch off and give the release branch a name reflecting the new version number:

$ git checkout -b release-1.2 develop Switched to a new branch "release-1.2" $ ./ 1.2 Files modified successfully, version bumped to 1.2. $ git commit -a -m "Bumped version number to 1.2" [release-1.2 74d9424] Bumped version number to 1.2 1 files changed, 1 insertions(+), 1 deletions(-)

After creating a new branch and switching to it, we bump the version number. Here, is a fictional shell script that changes some files in the working copy to reflect the new version. (This can of course be a manual change—the point being that some files change.) Then, the bumped version number is committed.

This new branch may exist there for a while, until the release may be rolled out definitely. During that time, bug fixes may be applied in this branch (rather than on the developbranch). Adding large new features here is strictly prohibited. They must be merged intodevelop, and therefore, wait for the next big release.

Finishing a release branch

When the state of the release branch is ready to become a real release, some actions need to be carried out. First, the release branch is merged into master (since every commit onmaster is a new release by definition, remember). Next, that commit on master must be tagged for easy future reference to this historical version. Finally, the changes made on the release branch need to be merged back into develop, so that future releases also contain these bug fixes.

The first two steps in Git:

$ git checkout master Switched to branch 'master' $ git merge --no-ff release-1.2 Merge made by recursive. (Summary of changes) $ git tag -a 1.2

The release is now done, and tagged for future reference.
Edit: You might as well want to use the -s or -u <key> flags to sign your tag cryptographically.

To keep the changes made in the release branch, we need to merge those back intodevelop, though. In Git:

$ git checkout develop Switched to branch 'develop' $ git merge --no-ff release-1.2 Merge made by recursive. (Summary of changes)

This step may well lead to a merge conflict (probably even, since we have changed the version number). If so, fix it and commit.

Now we are really done and the release branch may be removed, since we don’t need it anymore:

$ git branch -d release-1.2 Deleted branch release-1.2 (was ff452fe).

Hotfix branches

May branch off from: master
Must merge back into: develop and master
Branch naming convention: hotfix-*

Hotfix branches are very much like release branches in that they are also meant to prepare for a new production release, albeit unplanned. They arise from the necessity to act immediately upon an undesired state of a live production version. When a critical bug in a production version must be resolved immediately, a hotfix branch may be branched off from the corresponding tag on the master branch that marks the production version.

The essence is that work of team members (on the develop branch) can continue, while another person is preparing a quick production fix.

Creating the hotfix branch

Hotfix branches are created from the master branch. For example, say version 1.2 is the current production release running live and causing troubles due to a severe bug. But changes on develop are yet unstable. We may then branch off a hotfix branch and start fixing the problem:

$ git checkout -b hotfix-1.2.1 master Switched to a new branch "hotfix-1.2.1" $ ./ 1.2.1 Files modified successfully, version bumped to 1.2.1. $ git commit -a -m "Bumped version number to 1.2.1" [hotfix-1.2.1 41e61bb] Bumped version number to 1.2.1 1 files changed, 1 insertions(+), 1 deletions(-)

Don’t forget to bump the version number after branching off!

Then, fix the bug and commit the fix in one or more separate commits.

$ git commit -m "Fixed severe production problem" [hotfix-1.2.1 abbe5d6] Fixed severe production problem 5 files changed, 32 insertions(+), 17 deletions(-)

Finishing a hotfix branch

When finished, the bugfix needs to be merged back into master, but also needs to be merged back into develop, in order to safeguard that the bugfix is included in the next release as well. This is completely similar to how release branches are finished.

First, update master and tag the release.

$ git checkout master Switched to branch 'master' $ git merge --no-ff hotfix-1.2.1 Merge made by recursive. (Summary of changes) $ git tag -a 1.2.1

Edit: You might as well want to use the -s or -u <key> flags to sign your tag cryptographically.

Next, include the bugfix in develop, too:

$ git checkout develop Switched to branch 'develop' $ git merge --no-ff hotfix-1.2.1 Merge made by recursive. (Summary of changes)

The one exception to the rule here is that, when a release branch currently exists, the hotfix changes need to be merged into that release branch, instead ofdevelop. Back-merging the bugfix into the release branch will eventually result in the bugfix being merged into develop too, when the release branch is finished. (If work indevelop immediately requires this bugfix and cannot wait for the release branch to be finished, you may safely merge the bugfix into develop now already as well.)

Finally, remove the temporary branch:

$ git branch -d hotfix-1.2.1 Deleted branch hotfix-1.2.1 (was abbe5d6).


While there is nothing really shocking new to this branching model, the “big picture” figure that this post began with has turned out to be tremendously useful in our projects. It forms an elegant mental model that is easy to comprehend and allows team members to develop a shared understanding of the branching and releasing processes.

A high-quality PDF version of the figure is provided here. Go ahead and hang it on the wall for quick reference at any time.

Update: And for anyone who requested it: here’s the gitflow-model.src.key of the main diagram image (Apple Keynote).

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Branching and Merging Best Practices | Branching and Merging Guide


Branching and Merging Practices

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