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Git Common-Flow {{version}}
===========================
Introduction
------------
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](http://scottchacon.com/2011/08/31/github-flow.html) of
[GitHub Flow](https://guides.github.com/introduction/flow/), while taking into
account how a lot of open source projects most commonly use git.
In short, Common-Flow is essentially GitHub Flow with the addition of versioned
releases, optional release branches, and without the requirement to deploy to
production all the time.
Summary
-------
- The "main" branch is the mainline branch with latest changes, and must not be
broken.
- Changes (features, bugfixes, etc.) are done on "change branches" created from
the main branch.
- Rebase change branches [early and often](https://i.imgur.com/1RS8x2d.png).
- When a change branch is stable and ready, it is merged back in to main.
- A release is just a git tag who's name is the exact release version string
(e.g. "2.11.4").
- Release branches can be used to avoid change freezes on main. They are not
required, instead they are available if you need them.
Terminology
-----------
- **Main Branch** - Must be named "main", must always have passing tests, and is
not guaranteed to always work in production environments.
- **Change Branches** - Any branch that introduces changes like a new feature, a
bugfix, 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** - May be considered safe to use in production environments. Is
effectively just a git tag named after the version of the release.
- **Release Branches** - Used both for short-term preparations of a release, and
for long-term maintenance of older versions.
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](https://tools.ietf.org/html/rfc2119).
1. TL;DR
1. Do not break the main branch.
2. A release is a git tag.
2. The Main Branch
1. A branch named "main" MUST exist and it MUST be referred to as the "main
branch".
2. The main branch MUST always be in a non-broken state with its test suite
passing.
3. The main branch IS NOT guaranteed to always work in production
environments. Despite test suites passing it may at times contain
unfinished work. Only releases may be considered safe for production use.
4. The main branch SHOULD always be in a "as near as possibly ready for
release/production" state to reduce any friction with creating a new
release.
3. Change Branches
1. Each change (feature, bugfix, etc.) MUST be performed on separate
branches that SHOULD be referred to as "change branches".
2. All change branches MUST have descriptive names.
3. It is RECOMMENDED that you commit often locally, and that you try and
keep the commits reasonably structured to avoid a messy and confusing git
history.
4. You SHOULD regularly push your work to the same named branch on the
remote server.
5. You SHOULD create separate change branches for each distinctly different
change. You SHOULD NOT include multiple unrelated changes into a single
change branch.
6. 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.
7. 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.
8. After updating a change branch from its source branch you MUST push the
change branch to the remote server. Due to the nature of rebasing, you
will be required to do a force push, and you MUST use the
"--force-with-lease" git push option when doing so instead of the regular
"--force".
9. If there is a truly valid technical reason to not use rebase when
updating change branches, then you can update change branches via merge
instead of rebase. The decision to use merge MUST only be taken after all
possible options to use rebase have been tried and failed. People not
understanding how to use rebase is NOT a valid reason to use merge. If
you do decide to use merge instead of rebase, you MUST NOT use a mixture
of both methods, pick one and stick to it.
4. Pull Requests
1. To merge a change branch into its merge target, you MUST open a "pull
request" (or equivalent).
2. The purpose of a pull request is to allow others to review your changes
and give feedback. You can then fix any issues, complaints, and more that
might arise, and then let people review again.
3. Before creating a pull request, it is RECOMMENDED that you consider the
state of your change branch's commit history. If it is messy and
confusing, it might be a good idea to rebase your branch with "git rebase
-i" to present a cleaner and easier to follow commit history for your
reviewers.
4. 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 main branch.
5. To get feedback, help, or generally just discuss a change branch with
others, it is RECOMMENDED you create a pull request and discuss the
changes with others there. This leaves a clear and visible history of
how, when, and why the code looks and behaves the way it does.
5. Versioning
1. A "version string" is a typically mostly numeric string that identifies a
specific version of a project. The version string itself MUST NOT have a
"v" prefix, but the version string can be displayed with a "v" prefix to
indicate it is a version that is being referred to.
2. The source of truth for a project's version MUST be a git tag with a name
based on the version string. This kind of tag MUST be referred to as a
"release tag".
3. It is OPTIONAL, but RECOMMENDED to also keep the version string
hard-coded somewhere in the project code-base.
4. If you hard-code the version string into the code-base, it is RECOMMENDED
that you do so in a file called "VERSION" located in the root of the
project. But be mindful of the conventions of your programming language
and community when choosing if, where and how to hard-code the version
string.
5. If you are using a "VERSION" file in the root of the project, this file
MUST only contain the exact version string, meaning it MUST NOT have a
"v" prefix. For example, "v2.11.4" is bad, and "2.11.4" is good.
6. It is OPTIONAL, but RECOMMENDED that the version string follows Semantic
Versioning (<http://semver.org/>).
6. Releases
1. To create a new release, you MUST create a git tag named as the exact
version string of the release. This kind of tag MUST be referred to as a
"release tag".
2. The release tag name can OPTIONALLY be prefixed with "v". For example,
the tag name can be either "2.11.4" or "v2.11.4". It is however
RECOMMENDED that you do not use a "v" prefix. You MUST NOT use a mixture
of "v" prefixed and non-prefixed tags. Pick one form and stick to it.
3. If the version string is hard-coded into the code-base, you MUST create a
"version bump" commit which changes the hard-coded version string of the
project.
4. When using version bump commits, the release tag MUST be placed on the
version bump commit.
5. If you are not using a release branch, then the release tag, and if
relevant the version bump commit, MUST be created directly on the main
branch.
6. The version bump commit SHOULD have a commit message following the
Conventional Commits format. For example, "chore(release): 2.11.4" or
"chore: bump version to 2.11.4". Alternatively, a simple "Bump version to
2.11.4" format is acceptable.
7. 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.
8. If you use annotated release tags, the first line of the annotation
SHOULD read "Release VERSION". For example for version "2.11.4" the first
line of the tag annotation SHOULD read "Release 2.11.4". The second line
MUST be blank, and the changelog MUST start on the third line.
9. When using Conventional Commits, breaking changes MUST be indicated
either by appending "!" after the type/scope (e.g. "feat!:" or
"feat(api)!:"), or by including a "BREAKING CHANGE:" footer in the commit
message. Breaking changes correspond to a MAJOR version bump in Semantic
Versioning.
10. When using Conventional Commits along with Semantic Versioning, commits
of type "fix" correspond to PATCH releases, commits of type "feat"
correspond to MINOR releases, and commits with breaking changes
correspond to MAJOR releases. This alignment enables automated version
determination and changelog generation.
7. Short-Term Release Branches
1. Any branch that has a name starting with "release-" SHOULD be referred to
as a "release branch".
2. Any release branch which has a name ending with a specific version
string, MUST be referred to as a "short-term release branch".
3. Use of short-term release branches are OPTIONAL, and intended to be used
to create a specific versioned release.
4. A short-term release branch is RECOMMENDED if there is a lengthy
prerelease verification process to avoid a code freeze on the main
branch.
5. Short-term release branches MUST have a name of "release-VERSION". For
example for version "2.11.4" the release branch name MUST be
"release-2.11.4".
6. When using a short-term release branch to create a release, the release
tag and if used, version bump commit, MUST be placed directly on the
short-term release branch itself.
7. Only very minor changes should be performed on a short-term release
branch directly. Any larger changes SHOULD be done in the main branch,
and SHOULD be pulled into the release branch by rebasing it on top of the
main branch the same way a change branch pulls in updates from its source
branch.
8. After a release tag has been created, the release branch MUST be merged
back into its source branch and then deleted. Typically the source branch
will be the main branch.
8. Long-term Release Branches
1. Any release branch which has a name ending with a nonspecific version
string, MUST be referred to as a "long-term release branch". For example,
"release-2.11" is a long-term release branch, while "release-2.11.4" is a
short-term release branch.
2. Use of long-term release branches are OPTIONAL, and intended for work on
versions which are not currently part of the main branch. Typically this
is useful when you need to create a new maintenance release for an older
version.
3. A long-term release branch MUST have a name with a nonspecific version
number. For example, a long-term release branch for creating new 2.9.x
releases MUST be named "release-2.9".
4. Long-term release branches for maintenance releases of older versions
MUST be created from the relevant release tag. For example, if the main
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" from the "2.9.7" release tag. The security fix release will
then end up being version "2.9.8".
5. To create a new release from a long-term release branch, you MUST follow
the same process as a release from the main branch, except the long-term
release branch takes the place of the main branch.
6. A long-term release branch should be treated with the same respect as the
main branch. It is effectively the main branch for the release series in
question. Meaning it MUST always be in a non-broken state, MUST NOT be
force pushed to, etc.
9. Bug Fixes & Rollback
1. You MUST NOT under any circumstances force push to the main branch or to
long-term release branches.
2. If a change branch which has been merged into the main branch is found to
have a bug in it, the bugfix work MUST be done as a new separate change
branch. This new change branch MUST follow the same workflow as any other
change branch.
3. If a change branch is wrongfully merged into main, 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.
10. Git Best Practices
1. It is RECOMMENDED that all commit messages follow the Conventional
Commits specification (<https://www.conventionalcommits.org/>). This
provides a structured format that integrates well with Semantic
Versioning, and enables automated changelog generation. At minimum,
commit messages SHOULD follow the Commit Guidelines from the official git
documentation:
<https://git-scm.com/book/en/v2/Distributed-Git-Contributing-to-a-Project#_commit_guidelines>
2. You SHOULD never blindly commit all changes with "git commit -a". It is
RECOMMENDED you use "git add -i" or "git add -p" to add individual
changes to the staging area so you are fully aware of what you are
committing.
3. You SHOULD always use "--force-with-lease" when doing a force push. The
regular "--force" option is dangerous and destructive. More information:
<https://www.codestudy.net/blog/git-push-force-with-lease-vs-force/>
4. You SHOULD understand and be comfortable with rebasing:
<https://git-scm.com/book/en/v2/Git-Branching-Rebasing>
5. 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".
6. 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
main.
7. When using Conventional Commits, it is RECOMMENDED to use tooling to
automatically generate changelogs from commit messages. This pairs well
with the release process and ensures changelogs are consistent and
complete.
FAQ
---
### Why use Common-Flow instead of Git Flow, and how does it differ?
Common-Flow tries to be a lot less complicated than Git Flow by having fewer
types of branches, and simpler rules. Normal day to day development doesn't
really change much:
- You create change branches instead of feature branches, without the need of a
"feature/" or "change/" prefix in the branch name.
- Change branches are typically created from and merged back into "main" instead
of "develop".
- Creating a release is done by simply creating a git tag, typically on the main
branch.
In detail, the main differences between Git Flow and Common-Flow are:
- There is no "develop" branch, there is only a "main" branch which contains the
latest work. In Git Flow the main branch effectively ends up just being a
pointer to the latest release, despite the fact that Git Flow includes release
tags too. In Common-Flow you just look at the tags to find the latest release.
- There are no "feature" or "hotfix" branches, there's only "change" branches.
Any branch that is not main and introduces changes is a change branch. Change
branches also don't have an enforced naming convention, they just need to have
a "descriptive name". This makes things simpler and allows more flexibility.
- Release branches are available, but optional. Instead of enforcing the use of
release branches like Git Flow, Common-Flow only recommends the use of release
branches when it makes things easier. If creating a new release by tagging
"main" works for you, great, do that.
### Why use Common-Flow instead of GitHub Flow, and how does it differ?
Common-Flow is essentially GitHub Flow with the addition of a "Release" concept
that uses tags. It also attempts to define how certain common tasks are done,
like updating change/feature branches from their source branches for example.
This is to help end arguments about how such things are done.
If a deployment/release for you is just getting the latest code in the main
branch out without caring about bumping version numbers, GitHub Flow is a good
fit for you. You probably don't need the extras of Common-Flow.
However, if your deployments/releases have specific version numbers, then
Common-Flow gives you a simple set of rules for how to create and manage
releases, on top of what GitHub Flow already does.
### What does "descriptive name" mean for change branches?
It means what it sounds like. The name should be descriptive, as in by just
reading the name of the branch you should understand what the branch's purpose
is and what it does. Here's a few examples:
- add-2fa-support
- fix-login-issue
- remove-sort-by-middle-name-functionality
- update-font-awesome
- change-search-behavior
- improve-pagination-performance
- tweak-footer-style
Notice how none of these have any prefixes like "feature/" or "hotfix/", they're
not needed when branch names are properly descriptive. However, there's nothing
to say you can't use such prefixes if you want.
You can also add ticket numbers to the branch name if your team/org has that as
part of its process. But it is recommended that ticket numbers are added to the
end of the branch name. The ticket number is essentially metadata, so put it at
the end and out of the way of humans trying to read the descriptive name from
left to right.
### How do we release an emergency hotfix when the main branch is broken?
This should ideally never happen, however if it does you can do one of the
following:
- Review why the main branch is broken and revert the changes that caused the
issues. Then apply the hotfix and release.
- Or use a short-term release branch created from the latest release tag instead
of the main branch. Apply the hotfix to the release branch, create a release
tag on the release branch, and then merge it back into main.
In this situation, it is recommended you try to revert the offending changes
that's preventing a new release from main. But if that proves to be a
complicated task and you're short on time, a short-term release branch gives you
an instant fix to the situation at hand. You can then resolve the issues with
the main branch later.
About
-----
The Git Common-Flow specification is authored by [Jim
Myhrberg](https://jimeh.me/).
If you'd like to leave feedback, please [open an issue on
GitHub](https://github.com/jimeh/common-flow/issues).
License
-------
[Creative Commons - CC BY 4.0](https://creativecommons.org/licenses/by/4.0/)
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