gitworkflows(7) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | SEPARATE CHANGES | MANAGING BRANCHES | DISTRIBUTED WORKFLOWS | SEE ALSO | GIT | COLOPHON

GITWORKFLOWS(7)                Git Manual                GITWORKFLOWS(7)

NAME         top

       gitworkflows - An overview of recommended workflows with Git

SYNOPSIS         top

       git *

DESCRIPTION         top

       This document attempts to write down and motivate some of the
       workflow elements used for git.git itself. Many ideas apply in
       general, though the full workflow is rarely required for smaller
       projects with fewer people involved.

       We formulate a set of rules for quick reference, while the prose
       tries to motivate each of them. Do not always take them
       literally; you should value good reasons for your actions higher
       than manpages such as this one.

SEPARATE CHANGES         top

       As a general rule, you should try to split your changes into
       small logical steps, and commit each of them. They should be
       consistent, working independently of any later commits, pass the
       test suite, etc. This makes the review process much easier, and
       the history much more useful for later inspection and analysis,
       for example with git-blame(1) and git-bisect(1).

       To achieve this, try to split your work into small steps from the
       very beginning. It is always easier to squash a few commits
       together than to split one big commit into several. Don’t be
       afraid of making too small or imperfect steps along the way. You
       can always go back later and edit the commits with git rebase
       --interactive before you publish them. You can use git stash push
       --keep-index to run the test suite independent of other
       uncommitted changes; see the EXAMPLES section of git-stash(1).

MANAGING BRANCHES         top

       There are two main tools that can be used to include changes from
       one branch on another: git-merge(1) and git-cherry-pick(1).

       Merges have many advantages, so we try to solve as many problems
       as possible with merges alone. Cherry-picking is still
       occasionally useful; see "Merging upwards" below for an example.

       Most importantly, merging works at the branch level, while
       cherry-picking works at the commit level. This means that a merge
       can carry over the changes from 1, 10, or 1000 commits with equal
       ease, which in turn means the workflow scales much better to a
       large number of contributors (and contributions). Merges are also
       easier to understand because a merge commit is a "promise" that
       all changes from all its parents are now included.

       There is a tradeoff of course: merges require a more careful
       branch management. The following subsections discuss the
       important points.

   Graduation
       As a given feature goes from experimental to stable, it also
       "graduates" between the corresponding branches of the software.
       git.git uses the following integration branches:

       •   maint tracks the commits that should go into the next
           "maintenance release", i.e., update of the last released
           stable version;

       •   master tracks the commits that should go into the next
           release;

       •   next is intended as a testing branch for topics being tested
           for stability for master.

       There is a fourth official branch that is used slightly
       differently:

       •   seen (patches seen by the maintainer) is an integration
           branch for things that are not quite ready for inclusion yet
           (see "Integration Branches" below).

       Each of the four branches is usually a direct descendant of the
       one above it.

       Conceptually, the feature enters at an unstable branch (usually
       next or seen), and "graduates" to master for the next release
       once it is considered stable enough.

   Merging upwards
       The "downwards graduation" discussed above cannot be done by
       actually merging downwards, however, since that would merge all
       changes on the unstable branch into the stable one. Hence the
       following:

       Example 1. Merge upwards

       Always commit your fixes to the oldest supported branch that
       requires them. Then (periodically) merge the integration branches
       upwards into each other.

       This gives a very controlled flow of fixes. If you notice that
       you have applied a fix to e.g. master that is also required in
       maint, you will need to cherry-pick it (using git-cherry-pick(1))
       downwards. This will happen a few times and is nothing to worry
       about unless you do it very frequently.

   Topic branches
       Any nontrivial feature will require several patches to implement,
       and may get extra bugfixes or improvements during its lifetime.

       Committing everything directly on the integration branches leads
       to many problems: Bad commits cannot be undone, so they must be
       reverted one by one, which creates confusing histories and
       further error potential when you forget to revert part of a group
       of changes. Working in parallel mixes up the changes, creating
       further confusion.

       Use of "topic branches" solves these problems. The name is pretty
       self explanatory, with a caveat that comes from the "merge
       upwards" rule above:

       Example 2. Topic branches

       Make a side branch for every topic (feature, bugfix, ...). Fork
       it off at the oldest integration branch that you will eventually
       want to merge it into.

       Many things can then be done very naturally:

       •   To get the feature/bugfix into an integration branch, simply
           merge it. If the topic has evolved further in the meantime,
           merge again. (Note that you do not necessarily have to merge
           it to the oldest integration branch first. For example, you
           can first merge a bugfix to next, give it some testing time,
           and merge to maint when you know it is stable.)

       •   If you find you need new features from the branch other to
           continue working on your topic, merge other to topic.
           (However, do not do this "just habitually", see below.)

       •   If you find you forked off the wrong branch and want to move
           it "back in time", use git-rebase(1).

       Note that the last point clashes with the other two: a topic that
       has been merged elsewhere should not be rebased. See the section
       on RECOVERING FROM UPSTREAM REBASE in git-rebase(1).

       We should point out that "habitually" (regularly for no real
       reason) merging an integration branch into your topics — and by
       extension, merging anything upstream into anything downstream on
       a regular basis — is frowned upon:

       Example 3. Merge to downstream only at well-defined points

       Do not merge to downstream except with a good reason: upstream
       API changes affect your branch; your branch no longer merges to
       upstream cleanly; etc.

       Otherwise, the topic that was merged to suddenly contains more
       than a single (well-separated) change. The many resulting small
       merges will greatly clutter up history. Anyone who later
       investigates the history of a file will have to find out whether
       that merge affected the topic in development. An upstream might
       even inadvertently be merged into a "more stable" branch. And so
       on.

   Throw-away integration
       If you followed the last paragraph, you will now have many small
       topic branches, and occasionally wonder how they interact.
       Perhaps the result of merging them does not even work? But on the
       other hand, we want to avoid merging them anywhere "stable"
       because such merges cannot easily be undone.

       The solution, of course, is to make a merge that we can undo:
       merge into a throw-away branch.

       Example 4. Throw-away integration branches

       To test the interaction of several topics, merge them into a
       throw-away branch. You must never base any work on such a branch!

       If you make it (very) clear that this branch is going to be
       deleted right after the testing, you can even publish this
       branch, for example to give the testers a chance to work with it,
       or other developers a chance to see if their in-progress work
       will be compatible. git.git has such an official throw-away
       integration branch called seen.

   Branch management for a release
       Assuming you are using the merge approach discussed above, when
       you are releasing your project you will need to do some
       additional branch management work.

       A feature release is created from the master branch, since master
       tracks the commits that should go into the next feature release.

       The master branch is supposed to be a superset of maint. If this
       condition does not hold, then maint contains some commits that
       are not included on master. The fixes represented by those
       commits will therefore not be included in your feature release.

       To verify that master is indeed a superset of maint, use git log:

       Example 5. Verify master is a superset of maint

       git log master..maint

       This command should not list any commits. Otherwise, check out
       master and merge maint into it.

       Now you can proceed with the creation of the feature release.
       Apply a tag to the tip of master indicating the release version:

       Example 6. Release tagging

       git tag -s -m "Git X.Y.Z" vX.Y.Z master

       You need to push the new tag to a public Git server (see
       "DISTRIBUTED WORKFLOWS" below). This makes the tag available to
       others tracking your project. The push could also trigger a
       post-update hook to perform release-related items such as
       building release tarballs and preformatted documentation pages.

       Similarly, for a maintenance release, maint is tracking the
       commits to be released. Therefore, in the steps above simply tag
       and push maint rather than master.

   Maintenance branch management after a feature release
       After a feature release, you need to manage your maintenance
       branches.

       First, if you wish to continue to release maintenance fixes for
       the feature release made before the recent one, then you must
       create another branch to track commits for that previous release.

       To do this, the current maintenance branch is copied to another
       branch named with the previous release version number (e.g.
       maint-X.Y.(Z-1) where X.Y.Z is the current release).

       Example 7. Copy maint

       git branch maint-X.Y.(Z-1) maint

       The maint branch should now be fast-forwarded to the newly
       released code so that maintenance fixes can be tracked for the
       current release:

       Example 8. Update maint to new releasegit checkout maintgit merge --ff-only master

       If the merge fails because it is not a fast-forward, then it is
       possible some fixes on maint were missed in the feature release.
       This will not happen if the content of the branches was verified
       as described in the previous section.

   Branch management for next and seen after a feature release
       After a feature release, the integration branch next may
       optionally be rewound and rebuilt from the tip of master using
       the surviving topics on next:

       Example 9. Rewind and rebuild nextgit switch -C next mastergit merge ai/topic_in_next1git merge ai/topic_in_next2

       •   ...

       The advantage of doing this is that the history of next will be
       clean. For example, some topics merged into next may have
       initially looked promising, but were later found to be
       undesirable or premature. In such a case, the topic is reverted
       out of next but the fact remains in the history that it was once
       merged and reverted. By recreating next, you give another
       incarnation of such topics a clean slate to retry, and a feature
       release is a good point in history to do so.

       If you do this, then you should make a public announcement
       indicating that next was rewound and rebuilt.

       The same rewind and rebuild process may be followed for seen. A
       public announcement is not necessary since seen is a throw-away
       branch, as described above.

DISTRIBUTED WORKFLOWS         top

       After the last section, you should know how to manage topics. In
       general, you will not be the only person working on the project,
       so you will have to share your work.

       Roughly speaking, there are two important workflows: merge and
       patch. The important difference is that the merge workflow can
       propagate full history, including merges, while patches cannot.
       Both workflows can be used in parallel: in git.git, only
       subsystem maintainers use the merge workflow, while everyone else
       sends patches.

       Note that the maintainer(s) may impose restrictions, such as
       "Signed-off-by" requirements, that all commits/patches submitted
       for inclusion must adhere to. Consult your project’s
       documentation for more information.

   Merge workflow
       The merge workflow works by copying branches between upstream and
       downstream. Upstream can merge contributions into the official
       history; downstream base their work on the official history.

       There are three main tools that can be used for this:

       •   git-push(1) copies your branches to a remote repository,
           usually to one that can be read by all involved parties;

       •   git-fetch(1) that copies remote branches to your repository;
           and

       •   git-pull(1) that does fetch and merge in one go.

       Note the last point. Do not use git pull unless you actually want
       to merge the remote branch.

       Getting changes out is easy:

       Example 10. Push/pull: Publishing branches/topics

       git push <remote> <branch> and tell everyone where they can fetch
       from.

       You will still have to tell people by other means, such as mail.
       (Git provides the git-request-pull(1) to send preformatted pull
       requests to upstream maintainers to simplify this task.)

       If you just want to get the newest copies of the integration
       branches, staying up to date is easy too:

       Example 11. Push/pull: Staying up to date

       Use git fetch <remote> or git remote update to stay up to date.

       Then simply fork your topic branches from the stable remotes as
       explained earlier.

       If you are a maintainer and would like to merge other people’s
       topic branches to the integration branches, they will typically
       send a request to do so by mail. Such a request looks like

           Please pull from
               <url> <branch>

       In that case, git pull can do the fetch and merge in one go, as
       follows.

       Example 12. Push/pull: Merging remote topics

       git pull <url> <branch>

       Occasionally, the maintainer may get merge conflicts when they
       try to pull changes from downstream. In this case, they can ask
       downstream to do the merge and resolve the conflicts themselves
       (perhaps they will know better how to resolve them). It is one of
       the rare cases where downstream should merge from upstream.

   Patch workflow
       If you are a contributor that sends changes upstream in the form
       of emails, you should use topic branches as usual (see above).
       Then use git-format-patch(1) to generate the corresponding emails
       (highly recommended over manually formatting them because it
       makes the maintainer’s life easier).

       Example 13. format-patch/am: Publishing branches/topicsgit format-patch -M upstream..topic to turn them into
           preformatted patch files

       •   git send-email --to=<recipient> <patches>

       See the git-format-patch(1) and git-send-email(1) manpages for
       further usage notes.

       If the maintainer tells you that your patch no longer applies to
       the current upstream, you will have to rebase your topic (you
       cannot use a merge because you cannot format-patch merges):

       Example 14. format-patch/am: Keeping topics up to date

       git pull --rebase <url> <branch>

       You can then fix the conflicts during the rebase. Presumably you
       have not published your topic other than by mail, so rebasing it
       is not a problem.

       If you receive such a patch series (as maintainer, or perhaps as
       a reader of the mailing list it was sent to), save the mails to
       files, create a new topic branch and use git am to import the
       commits:

       Example 15. format-patch/am: Importing patches

       git am < patch

       One feature worth pointing out is the three-way merge, which can
       help if you get conflicts: git am -3 will use index information
       contained in patches to figure out the merge base. See git-am(1)
       for other options.

SEE ALSO         top

       gittutorial(7), git-push(1), git-pull(1), git-merge(1),
       git-rebase(1), git-format-patch(1), git-send-email(1), git-am(1)

GIT         top

       Part of the git(1) suite

COLOPHON         top

       This page is part of the git (Git distributed version control
       system) project.  Information about the project can be found at
       ⟨http://git-scm.com/⟩.  If you have a bug report for this manual
       page, see ⟨http://git-scm.com/community⟩.  This page was obtained
       from the project's upstream Git repository
       ⟨https://github.com/git/git.git⟩ on 2021-04-01.  (At that time,
       the date of the most recent commit that was found in the
       repository was 2021-03-30.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

Git 2.31.1.163.ga65ce7         04/01/2021                GITWORKFLOWS(7)

Pages that refer to this page: git(1)git-cherry(1)gittutorial(7)