Git Common-Flow 1.0.0-rc.2
Common-Flow is an attempt to gather a sensible selection of the most common usage patterns of git into a single and concise specification. It is based on the original variant of GitHub Flow, while taking into account how a lot of open source projects use git.
TL;DR: Common-Flow is basically GitHub Flow with the addition of versioned releases, maintenance releases for old versions, and without the requirement to deploy to production all the time.
- Master Branch - Must always have passing tests, is considered bleeding
edge, and must be named
- Change Branches - Any branch that introduces changes like a new feature, a bug fix, etc.
- Source Branch - The branch that a change branch was created from. New changes in the source branch should be incorporated into the change branch via rebasing.
- Merge Target - A branch that is the intended merge target for a change branch. Typically the merge target branch will be the same as the source branch.
- Pull Request - A means of requesting that a change branch is merged in to its merge target, allowing others to review, discuss and approve the changes.
- Release - Consists of a version bump commit, and a git tag named according to the new version string placed on said commit.
- Release Branches - Used both for short-term preparations of a release, and also for long-term maintenance of older version.
Git Common-Flow Specification (Common-Flow)
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.
- The Master Branch
- A branch named "master" MUST exist and it MUST be referred to as the "master branch".
- The master branch MUST be considered bleeding edge.
- The master branch MUST always be in a non-broken state with its test suite passing.
- The master branch SHOULD always be in a "as near as possibly ready for release/production" state to reduce any friction with creating a new release.
- Change Branches
- Each change (feature, bugfix, etc.) MUST be performed on separate branches that SHOULD be referred to as "change branches". All change branches MUST have descriptive names. It is RECOMMENDED that you commit often locally, and you SHOULD regularly push your work to the same named branch on the remote server.
- You MUST create separate change branches for each distinctly different change. You MUST NOT include multiple unrelated changes into a single change branch.
- When a change branch is created, the branch that it is created from SHOULD be referred to as the "source branch". Each change branch also needs a designated "merge target" branch, typically this will be the same as the source branch.
- Change branches MUST be regularly updated with any changes from their source branch. This MUST be done by rebasing the change branch on top of the source branch.
- After rebasing a change branch on top of its source branch you MUST push the change branch to the remote server. This will require you to do a force push, and you SHOULD use the "--force-with-lease" git push option.
- Pull Requests
- To merge a change branch into its merge target, you MUST open a "pull request" (or equivalent) so others can review and approve your changes.
- A pull request MUST only be merged when the change branch is up-to-date with its source branch, the test suite is passing, and you and others are happy with the change. This is especially important if the merge target is the master branch.
- To get feedback, help, or generally just discuss a change branch with others, the RECOMMENDED way to do so is by creating a pull request and discuss the changes with others there.
- The project MUST have its version hard-coded somewhere in the code-base. It is RECOMMENDED that this is done in a file called "VERSION" located in the root of the project.
- If you are using a "VERSION" file in the root of the project, this MUST only contain the exact version string.
- The version string SHOULD follow the Semantic Versioning (http://semver.org/) format. Use of Semantic Versioning is OPTIONAL, but the version string MUST NOT have a "v" prefix. For example "v2.11.4" is bad, and "2.11.4" is good.
- To create a new release, you MUST create a "version bump" commit which changes the hard-coded version string of the project. The version bump commit MUST have a git tag created on it and named as the exact version string.
- If you are not using a release branch, then the version bump commit MUST be created directly on the master branch.
- The version bump commit MUST have a commit message title of "Bump version to VERSION". For example, if the new version string is "2.11.4", the first line of the commit message MUST read: "Bump version to 2.11.4"
- The release tag on the version bump commit MUST be named exactly the same as the version string. The tag name can OPTIONALLY be prefixed with "v". For example the tag name can be either "2.11.4" or "v2.11.4". You MUST not use a mix of "v" prefixed and non-prefixed tags. Pick one form and stick to it.
- It is RECOMMENDED that release tags are lightweight tags, but you can OPTIONALLY use annotated tags if you want to include changelog information in the release tag itself.
- If you use annotated release tags, the first line of the annotation MUST read "Release VERSION". For example for version "2.11.4" the first line of the tag annotation would read "Release 2.11.4". The second line must be blank, and the changelog MUST start on the third line.
- Release Branches
- Any branch that has a name starting with "release-" SHOULD be referred to as a "release branch".
- Use of release branches is OPTIONAL.
- Changes in a release branch SHOULD typically come from work being done against the master branch. Meaning changes SHOULD only trickle downwards from the master branch. If a change needs to trickle back up into the master branch, that work should have happened against the master branch in the first place. One exception to this is version bump commits.
- There are two types of release branches; short-term, and long-term.
- Short-Term Release Branches
- Used for creating a specific versioned release.
- A short-term release branch is RECOMMENDED if there is a lengthy pre-release verification process to avoid a code freeze on the master branch.
- MUST have a name of "release-VERSION". For example for version "2.11.4" the release branch name MUST be "release-2.11.4".
- When using a short-term release branch, the version bump commit and release tag MUST be made directly on the release branch itself.
- Only very minor changes should be performed on a short-term release branch directly. Any larger changes SHOULD be done in the master branch, and SHOULD be pulled into the release branch by rebasing it on top of the master branch the same way a change branch pulls in updates from its source branch.
- After the version bump commit and release tag have been created, the release branch MUST be merged back into its source branch and then deleted. Typically the source branch will be the master branch.
- Long-Term Release Branches
- Used for work on versions which are not currently part of the master branch. Typically this is useful when you need to create a new maintenance release for a older version.
- The branch name MUST have a non-specific version number. For example a long-term release branch for creating new 2.9.x releases would be named "release-2.9".
- To create a new release from a long-term release branch, you MUST create a version bump commit and release tag directly on the release branch.
- A long-term release branch MUST be created from the relevant release tag. For example if the master branch is on version 2.11.4 and there is a security fix for all 2.9.x releases, the latest of which is "2.9.7". Create a new branch called "release-2.9" off of the "2.9.7" release tag. The security fix release will then end up being version "2.9.8".
- Bug Fixes & Rollback
- You MUST NOT under any circumstances force push to the master branch.
- If a change branch which has been merged into the master branch is found to have a bug in it, the bug fix work MUST be done as a new separate change branch and MUST follow the same workflow as any other change branch.
- If a change branch is wrongfully merged into master, or for any other reason the merge must be undone, you MUST undo the merge by reverting the merge commit itself. Effectively creating a new commit that reverses all the relevant changes.
- Git Best Practices
- All commit messages SHOULD follow the Commit Guidelines and format from the official git documentation: https://git-scm.com/book/en/v2/Distributed-Git-Contributing-to-a-Project
- You SHOULD never blindly commit all changes with "git commit -a". It is RECOMMENDED you use "git add -i" to add individual changes to the staging area so you are fully aware of what you are committing.
- You SHOULD always use "--force-with-lease" when doing a force push. The regular "--force" option is dangerous and destructive. More information: https://developer.atlassian.com/blog/2015/04/force-with-lease/
- You SHOULD understand and be comfortable with rebasing: https://git-scm.com/book/en/v2/Git-Branching-Rebasing
- It is RECOMMENDED that you always do "git pull --rebase" instead of "git pull" to avoid unnecessary merge commits. You can make this the default behavior of "git pull" with "git config --global pull.rebase true".
- It is RECOMMENDED that all branches be merged using "git merge --no-ff". This makes sure the reference to the original branch is kept in the commits, allows one to revert a merge by reverting a single merge commit, and creates a merge commit to mark the integration of the branch with master.
The Git Common-Flow specification is authored by Jim Myhrberg.
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