gitworkflows - An overview of recommended workflows with Git


   git *


   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


   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 save --keep-index to run the test suite independent
   of other uncommitted changes; see the EXAMPLES section of git-stash(1).


   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.

   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:

   *   pu (proposed updates) is an integration branch for things that are
       not quite ready for inclusion yet (see "Integration Branches"

   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
   pu), 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 require
   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

   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

   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

   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 pu.

   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 pu 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 checkout next

   *   git reset --hard 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 pu. A public
   announcement is not necessary since pu is a throw-away branch, as
   described above.


   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

   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

   Example 12. Push/pull: Merging remote topics

   git pull <url> <branch>

   Occasionally, the maintainer may get merge conflicts when he tries to
   pull changes from downstream. In this case, he 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

   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.


   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)


   Part of the git(1) suite.


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