Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
GITWORKFLOWS(7)			  Git Manual		       GITWORKFLOWS(7)

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 save --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:

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

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

       o   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:

       o   pu (proposed	updates) 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
       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
       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:

       o   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.)

       o   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.)

       o   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 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

       o   git checkout	maint

       o   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

       o   git checkout	next

       o   git reset --hard master

       o   git merge ai/topic_in_next1

       o   git merge ai/topic_in_next2

       o   ...

       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.

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:

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

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

       o   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 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

       o   git format-patch -M upstream..topic to turn them into preformatted
	   patch files

       o   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
       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
       Part of the git(1) suite

Git 2.13.2			  06/24/2017		       GITWORKFLOWS(7)

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

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=gitworkflows&sektion=7&manpath=FreeBSD+12.0-RELEASE+and+Ports>

home | help