# gitworkflows

## NAME



           gitworkflows - An overview of recommended workflows with Git
    


## SYNOPSIS



           git *
    


## DESCRIPTION



           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



           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



           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 release**
    
           •   **git checkout maint**
    
           •   **git 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 next**
    
           •   **git switch -C next master**
    
           •   **git merge ai/topic_in_next1**
    
           •   **git 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



           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/topics**
    
           •   **git 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.
    


## GIT



           Part of the git(1) suite
    


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