Git-Flow

Overview

Git-Flow is a high-level command set wrapping low-level Git commands to support the "successful branching model" (see http://nvie.com/posts/a-successful-git-branching-model/). It reduces the workflow steps necessary for the user.

To achieve this, Git-Flow assigns a special meaning to its branches. For Git-Flow, there are two main branches which live forever, the ‘develop‘ and ‘master‘ branch.

Develop Branch

The single ‘develop‘ branch (named by default develop) contains the ongoing development line. It contains all finished improvements and fixes.

Master Branch

The single ‘master‘ branch (named by default master) contains the stable release line. Its HEAD represents the latest stable release.

Other branches usually exist only for a certain period of time.

Feature Branches

For each new (non-trivial) improvement which should be added to the ongoing development line, a separate ‘feature‘ branch is created (named by default, e.g. feature/my-feature). This temporary branch will be used to work independently on this particular improvement (‘feature‘). If one thinks the feature is done, the commits from the ‘feature‘ branch are integrated (either merged or rebased) into the develop branch and the feature branch will usually be deleted. This way all feature branches in a repository indicate the features which are currently worked on.

o ... [> develop] merged feature A
| \
|  o ... a feature commit
|  |
o  | ... a develop commit
| /
o  ... another develop commit

Release Branches

To prepare a (planned) software release, a temporary ‘release‘ branch is created from the develop branch. The ‘release‘ branch is usually forked when all features for the upcoming release have been implemented and the develop branch is in ‘feature-freeze‘ state. Thus, it makes the release independent of further improvements of the develop branch and hence allows to ‘harden‘ the release by fixing bugs. When the state of this branch is ready for official release, it will be tagged and merged into both the master and the develop branch, this way creating a new release build to be made available to your customers (e.g. ‘version 4‘). After successful merging, the release branch usually is deleted.

o ... [> develop] merged release 4_0
| \
|  \   o ... [master] ... release 4_0
|   |/ |
|   o  | ... <tag/release-4_0_0] a release-preparing commit (e.g. bug-fix)
|   |  |
o  /   | ... a develop commit for a future release
| /    |
o      | ... another develop commit
|      |
|      o ... release 3_0_9
|     /|

Hotfix Branches

If after an official release a serious bug is detected, a ‘hotfix‘ branch will be created from the latest release state (the HEAD of the master branch). After fixing the bug(s) in this hotfix branch, the state will be tagged and merged into both the master and the develop branch, this way creating a new build to be made available to your customers (bugfix release, e.g. ‘version 4.0.1‘). After successful merging, the hotfix branch usually is deleted.

o ... [> develop] merged hotfix 4_0_1
| \
|  \   o ... [master] ... release 4_0_1
|   |/ |
|   o  | ... <tag/release-4_0_1] a serious bug-fix
|   |  |
o    \ | ... a develop commit for a future release
|     \|
|      o ... release 4_0
|     /|

Support Branches

Support branches are still in ‘experimental‘ state, according to the Git-Flow documentation. Nevertheless, they are used if you have multiple older releases (e.g. ‘version 3.0.*‘) which are still supported while the head of the master represents the latest release (e.g. ‘version 4.0.*‘). Changes in support branches may be unique to the support branch, because the code in the latest release is not present anymore or the bug/improvement has been implemented there already. If a commit from a support branch should still be integrated into the latest release, open a hotfix branch, cherry-pick the commit and finish the hotfix.

Usually, feature branches are created by developers, whereas release, hotfix and support branches are created by the release manager.

Git-Flow Commands

Configure

Use this command before starting to use Git-Flow. You can use the default branch naming or change it according to your needs. This will write the Git-Flow configuration to .git/config of your repository.

Here you can change the name of your Develop Branch and Master Branch, though it‘s strongly recommended to keep the defaults. In case you have multiple remote repositories configured, you can use Remotes to select which of the remote repositories should be used by Git-Flow. In the Prefixes section you can specify which prefix should be used for Feature-, Release-, Hotfix- and Support-branches. Having a sub-directory per category, is recommended. Version Tags specifies the prefix for tags which will be created when finishing a Release or Hotfix. Usually, it will be fine to use no prefix, as this will give you nice and simple tag names, like 4.6.1.

If there is a .gitflow file in the root of your working tree, the default values will be read from this file. When cloning a repository which already contains the .gitflow file, Git-Flow will be initialized automatically. This allows a quick Git-Flow configuration for each of your team-members even if you use a non-default Git-Flow branch naming scheme.

Start Feature

Use this command to start the work on a new feature. After providing a name for the feature, the corresponding feature branch will be forked off the develop branch and this new feature branch will be checked out.

Finish Feature

Use this command if you have committed your changes necessary for the feature and want to integrate them into main development line. There are 3 ways of doing this: by creating a merge commit (your feature commits will be preserved), by creating a simple commit (all your feature commits will be squashed into one commit) or by using rebase (your feature commits will be re-created on top of the develop branch). When merging or squashing, you need to enter the commit message for the new commit. Usually, you need to push the develop branch later.

Integrate Develop

If new commits were created in the develop branch after you‘ve created a feature branch, you may use this command to get the changes from the develop branch into your feature branch. You have the choice between using merge (which will create a merge commit in your feature branch) or rebase (your feature branch commits will be re-created on top of the latest develop commit).

The default operation is determined from your repository settings (Project|Repository Settings). Rebasing might not be available in case of merge commits, though.

Start Hotfix

Use this command to prepare a new bugfix release version from the latest release version (HEAD of the master branch) without using any new changes from the develop branch. This will create a hotfix branch from the master branch using the given hotfix name.

Finish Hotfix

Use this command if you have prepared some changes for the new bugfix release version and want to make it publicly available. This will tag the hotfix branch, merge it to the master and develop branch.

Start Release

Use this command to prepare a release, independent of further changes in the develop branch. This will create a release branch from the develop branch using the given release name.

Finish Release

Use this command if you have prepared changes for the release and want to make it publicly available. This will tag the release branch, merge it into the master and develop branch.

Start Support Branch

Use this command to create a support branch from the master branch. There is no corresponding Finish Support command available, as support branches live forever.

Migrating from the ‘master-release-branch‘ workflow

A common workflow and repository structure is to have a master in which all development takes place and once it comes to a release of the software, a release-branch is forked off from the master. This release-branch represents the stable (production-ready) state of the software at its current version, lives forever and all bug-fixing for this specific software version happens in that release-branch only. From time to time the release branch is merged into the master.

Migration

Let‘s assume a project which has an active master and release branches release-1 ... release-4 for the already released versions 1 ... 4 of the software. A good occasion to switch to Git-Flow will be immediately before the release of upcoming version 5:

• Fork develop from master and tell all your team-members to continue their development in develop. Directly committing to master is not allowed anymore.
• When the development of version 5 is in feature-freeze state, start a Release branch called release/5 , continue with work on the next version 6 in develop, bring release/5 to production quality and finally ‘finish‘ the release.

The mapping from the old master to the Git-Flow develop-branch is straight-forward. The interesting point now is how to proceed with bug-fixes for already released versions:

Old release branches become ‘support‘ branches

The old branches release-1 ... release-4 are actually Support branches and should be renamed to support/release-1 ... support/release-4, hence.

Usage

Once the branches have been migrated, you now can adopt the Git-Flow branching model, which does not know about long-living release-branches anymore.

Hotfix branches are used instead of a ‘current-release‘ branch

Once the first problem needs to be fixed for version 5, start a hotfix branch called hotfix/5.0.1 and apply the fix there. The hotfix/5.0.1 branch will remain open until you decide to officially release bug-fix version 5.0.1. Only then, this hotfix will be finished what results in a corresponding merge commit in master. Once a new problem needs to be fixed in version 5 series, create a new hotfix from hotfix/5.0.2 which will automatically be forked off the 5.0.1 merge commit in master. In this way, your master will proceed from version 5 release, to 5.0.1, 5.0.2, ...

If there is a serious problem in e.g. version 5.0.2, which needs to be fixed immediately and hotfix/5.0.3 is already in progress, do the following:

• start another hotfix branch hotfix/5.0.2a, which is forked off from 5.0.2 commit of master, as hotfix/5.0.3 is,
• apply the fix and
• finish the hotfix/5.0.2a immediately (and make the 5.0.2a version of the software public)

Now, master will contain a top-most 5.0.2a commit, derived from 5.0.2 commit. When finishing hotfix/5.0.3, the resulting 5.0.3 commit in master will be derived from the 5.0.2a and have the hotfix/5.0.3 merged in, i.e. it will represent the changes from both versions, 5.0.2a and 5.0.3. That‘s exactly what you would like to release now as 5.0.3 version.

Maintaining older versions

Hopefully, you won‘t need to apply many changes to older released versions. If you still need to, apply these changes to the corresponding support/release- branches and decide whether these changes should go into the current release as well: if not, you are all set now. If they should, cherry-pick the corresponding commits into the latest hotfix/5.0.x branch. There should be one such branch only, anyway. In this way, the changes will make it to master and develop later, when the hotfix is ‘finished‘.