Documentation/gitworkflows.txt - jrn/git - Git at Google

 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
 linkgit:git-blame[1] and linkgit: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 linkgit:git-stash[1].


 MANAGING BRANCHES
 -----------------

 There are two main tools that can be used to include changes from one
 branch on another: linkgit:git-merge[1] and
 linkgit: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:

 * '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:

 .Merge upwards
 [caption="Rule: "]
 =====================================
 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 linkgit: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:

 .Topic branches
 [caption="Rule: "]
 =====================================
 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 linkgit: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 linkgit: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:

 .Merge to downstream only at well-defined points
 [caption="Rule: "]
 =====================================
 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.

 .Throw-away integration branches
 [caption="Rule: "]
 =====================================
 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'.


 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:

 * linkgit:git-push[1] copies your branches to a remote repository,
   usually to one that can be read by all involved parties;

 * linkgit:git-fetch[1] that copies remote branches to your repository;
   and

 * linkgit: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:

 .Push/pull: Publishing branches/topics
 [caption="Recipe: "]
 =====================================
 `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 linkgit: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:

 .Push/pull: Staying up to date
 [caption="Recipe: "]
 =====================================
 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.

 .Push/pull: Merging remote topics
 [caption="Recipe: "]
 =====================================
 `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
 linkgit:git-format-patch[1] to generate the corresponding emails
 (highly recommended over manually formatting them because it makes the
 maintainer's life easier).

 .format-patch/am: Publishing branches/topics
 [caption="Recipe: "]
 =====================================
 * `git format-patch -M upstream..topic` to turn them into preformatted
   patch files
 * `git send-email --to=<recipient> <patches>`
 =====================================

 See the linkgit:git-format-patch[1] and linkgit: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):

 .format-patch/am: Keeping topics up to date
 [caption="Recipe: "]
 =====================================
 `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:

 .format-patch/am: Importing patches
 [caption="Recipe: "]
 =====================================
 `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 linkgit:git-am[1] for
 other options.


 SEE ALSO
 --------
 linkgit:gittutorial[7],
 linkgit:git-push[1],
 linkgit:git-pull[1],
 linkgit:git-merge[1],
 linkgit:git-rebase[1],
 linkgit:git-format-patch[1],
 linkgit:git-send-email[1],
 linkgit:git-am[1]

 GIT
 ---
 Part of the linkgit:git[1] suite.
	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
	linkgit:git-blame[1] and linkgit: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 linkgit:git-stash[1].


	MANAGING BRANCHES
	-----------------

	There are two main tools that can be used to include changes from one
	branch on another: linkgit:git-merge[1] and
	linkgit: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:

	* '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:

	.Merge upwards
	[caption="Rule: "]
	=====================================
	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 linkgit: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:

	.Topic branches
	[caption="Rule: "]
	=====================================
	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 linkgit: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 linkgit: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:

	.Merge to downstream only at well-defined points
	[caption="Rule: "]
	=====================================
	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.

	.Throw-away integration branches
	[caption="Rule: "]
	=====================================
	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'.


	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:

	* linkgit:git-push[1] copies your branches to a remote repository,
	usually to one that can be read by all involved parties;

	* linkgit:git-fetch[1] that copies remote branches to your repository;
	and

	* linkgit: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:

	.Push/pull: Publishing branches/topics
	[caption="Recipe: "]
	=====================================
	`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 linkgit: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:

	.Push/pull: Staying up to date
	[caption="Recipe: "]
	=====================================
	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.

	.Push/pull: Merging remote topics
	[caption="Recipe: "]
	=====================================
	`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
	linkgit:git-format-patch[1] to generate the corresponding emails
	(highly recommended over manually formatting them because it makes the
	maintainer's life easier).

	.format-patch/am: Publishing branches/topics
	[caption="Recipe: "]
	=====================================
	* `git format-patch -M upstream..topic` to turn them into preformatted
	patch files
	* `git send-email --to=<recipient> <patches>`
	=====================================

	See the linkgit:git-format-patch[1] and linkgit: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):

	.format-patch/am: Keeping topics up to date
	[caption="Recipe: "]
	=====================================
	`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:

	.format-patch/am: Importing patches
	[caption="Recipe: "]
	=====================================
	`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 linkgit:git-am[1] for
	other options.


	SEE ALSO
	--------
	linkgit:gittutorial[7],
	linkgit:git-push[1],
	linkgit:git-pull[1],
	linkgit:git-merge[1],
	linkgit:git-rebase[1],
	linkgit:git-format-patch[1],
	linkgit:git-send-email[1],
	linkgit:git-am[1]

	GIT
	---
	Part of the linkgit:git[1] suite.