This video covers How to use the advanced search bar What search operators are available How to input search queries directly How to better navigator your git history. GitHub is a web-based hosting service for projects that use the Git revision. The easiest, fastest, and most painless way of setting up a self-hosted Git service.
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Note of reflection (March 5, 2020)
This model was conceived in 2010, now more than 10 years ago, and not verylong after Git itself came into being. In those 10 years, git-flow (thebranching model laid out in this article) has become hugely popular in manya software team to the point where people have started treating it likea standard of sorts — but unfortunately also as a dogma or panacea.
During those 10 years, Git itself has taken the world by a storm, and themost popular type of software that is being developed with Git is shiftingmore towards web apps — at least in my filter bubble. Web apps are typicallycontinuously delivered, not rolled back, and you don't have to supportmultiple versions of the software running in the wild.
This is not the class of software that I had in mind when I wrote the blogpost 10 years ago. If your team is doing continuous delivery of software,I would suggest to adopt a much simpler workflow (like GitHubflow) instead of trying toshoehorn git-flow into your team.
If, however, you are building software that is explicitly versioned, or ifyou need to support multiple versions of your software in the wild, thengit-flow may still be as good of a fit to your team as it has been to peoplein the last 10 years. In that case, please read on.
To conclude, always remember that panaceas don't exist. Consider your owncontext. Don't be hating. Decide for yourself.
In this post I present the development model that I’ve introduced for some ofmy projects (both at work and private) about a year ago, and which has turnedout to be very successful. I’ve been meaning to write about it for a while now,but I’ve never really found the time to do so thoroughly, until now. I won’ttalk about any of the projects’ details, merely about the branching strategyand release management.
Why git? ¶
For a thorough discussion on the pros and cons of Git compared to centralizedsource code control systems, see theweb. There are plenty of flamewars going on there. As a developer, I prefer Git above all other tools aroundtoday. Git really changed the way developers think of merging and branching.From the classic CVS/Subversion world I came from, merging/branching has alwaysbeen considered a bit scary (“beware of merge conflicts, they bite you!”) andsomething you only do every once in a while.
But with Git, these actions are extremely cheap and simple, and they areconsidered one of the core parts of your daily workflow, really. For example,in CVS/Subversion books, branching and mergingis first discussed in the later chapters (for advanced users), while ineveryGitbook, it’s already covered in chapter3 (basics).
As a consequence of its simplicity and repetitive nature, branching and mergingare no longer something to be afraid of. Version control tools are supposed toassist in branching/merging more than anything else.
Enough about the tools, let’s head onto the development model. The model thatI’m going to present here is essentially no more than a set of procedures thatevery team member has to follow in order to come to a managed softwaredevelopment process.
Decentralized but centralized ¶
The repository setup that we use and that works well with this branching model,is that with a central “truth” repo. Note that this repo is only consideredto be the central one (since Git is a DVCS, there is no such thing as a centralrepo at a technical level). We will refer to this repo as
origin
, since thisname is familiar to all Git users.Each developer pulls and pushes to origin. But besides the centralizedpush-pull relationships, each developer may also pull changes from other peersto form sub teams. For example, this might be useful to work together with twoor more developers on a big new feature, before pushing the work in progress to
origin
prematurely. In the figure above, there are subteams of Alice and Bob,Alice and David, and Clair and David.Technically, this means nothing more than that Alice has defined a Git remote,named
bob
, pointing to Bob’s repository, and vice versa.The main branches ¶
At the core, the development model is greatly inspired by existing models outthere. The central repo holds two main branches with an infinite lifetime:
master
develop
The
master
branch at origin
should be familiar to every Git user. Parallelto the master
branch, another branch exists called develop
.We consider
origin/master
to be the main branch where the source code ofHEAD
always reflects a production-ready state.We consider
origin/develop
to be the main branch where the source code ofHEAD
always reflects a state with the latest delivered development changesfor the next release. Some would call this the “integration branch”. This iswhere any automatic nightly builds are built from.When the source code in the
develop
branch reaches a stable point and isready to be released, all of the changes should be merged back into master
somehow and then tagged with a release number. How this is done in detail willbe discussed further on.Therefore, each time when changes are merged back into
master
, this is a newproduction release by definition. We tend to be very strict at this, so thattheoretically, we could use a Git hook script to automatically build androll-out our software to our production servers everytime there was a commit onmaster
.Supporting branches ¶
Next to the main branches
master
and develop
, our development model usesa variety of supporting branches to aid parallel development between teammembers, ease tracking of features, prepare for production releases and toassist in quickly fixing live production problems. Unlike the main branches,these branches always have a limited life time, since they will be removedeventually.The different types of branches we may use are:
- Feature branches
- Release branches
- Hotfix branches
Each of these branches have a specific purpose and are bound to strict rules asto which branches may be their originating branch and which branches must betheir merge targets. We will walk through them in a minute.
By no means are these branches “special” from a technical perspective. Thebranch types are categorized by how we use them. They are of course plain oldGit branches.
Feature branches ¶
- May branch off from:
develop
- Must merge back into:
develop
- Branch naming convention:
- anything except
master
,develop
,release-*
, orhotfix-*
Feature branches (or sometimes called topic branches) are used to develop newfeatures for the upcoming or a distant future release. When startingdevelopment of a feature, the target release in which this feature will beincorporated may well be unknown at that point. The essence of a feature branchis that it exists as long as the feature is in development, but will eventuallybe merged back into
develop
(to definitely add the new feature to theupcoming release) or discarded (in case of a disappointing experiment).Feature branches typically exist in developer repos only, not in
origin
.Creating a feature branch ¶
When starting work on a new feature, branch off from the
develop
branch.Incorporating a finished feature on develop ¶
Finished features may be merged into the
develop
branch to definitely addthem to the upcoming release:The
--no-ff
flag causes the merge to always create a new commit object, evenif the merge could be performed with a fast-forward. This avoids losinginformation about the historical existence of a feature branch and groupstogether all commits that together added the feature. Compare:In the latter case, it is impossible to see from the Git history which of thecommit objects together have implemented a feature—you would have to manuallyread all the log messages. Reverting a whole feature (i.e. a group of commits),is a true headache in the latter situation, whereas it is easily done if the
--no-ff
flag was used.Yes, it will create a few more (empty) commit objects, but the gain is muchbigger than the cost.
Release branches ¶
- May branch off from:
develop
- Must merge back into:
develop
andmaster
- Branch naming convention:
release-*
Release branches support preparation of a new production release. They allowfor last-minute dotting of i’s and crossing t’s. Furthermore, they allow forminor bug fixes and preparing meta-data for a release (version number, builddates, etc.). By doing all of this work on a release branch, the
develop
branch is cleared to receive features for the next big release.The key moment to branch off a new release branch from
develop
is whendevelop (almost) reflects the desired state of the new release. At least allfeatures that are targeted for the release-to-be-built must be merged in todevelop
at this point in time. All features targeted at future releases maynot—they must wait until after the release branch is branched off.It is exactly at the start of a release branch that the upcoming release getsassigned a version number—not any earlier. Up until that moment, the
develop
branch reflected changes for the “next release”, but it is unclear whether that“next release” will eventually become 0.3 or 1.0, until the release branch isstarted. That decision is made on the start of the release branch and iscarried out by the project’s rules on version number bumping.Creating a release branch ¶
Release branches are created from the
develop
branch. For example, sayversion 1.1.5 is the current production release and we have a big releasecoming up. The state of develop
is ready for the “next release” and we havedecided that this will become version 1.2 (rather than 1.1.6 or 2.0). So webranch off and give the release branch a name reflecting the new versionnumber:After creating a new branch and switching to it, we bump the version number.Here,
bump-version.sh
is a fictional shell script that changes some files inthe working copy to reflect the new version. (This can of course be a manualchange—the point being that some files change.) Then, the bumped versionnumber is committed.This new branch may exist there for a while, until the release may be rolledout definitely. During that time, bug fixes may be applied in this branch(rather than on the
develop
branch). Adding large new features here isstrictly prohibited. They must be merged into develop
, and therefore, waitfor the next big release.Finishing a release branch ¶
When the state of the release branch is ready to become a real release, someactions need to be carried out. First, the release branch is merged into
master
(since every commit on master
is a new release by definition,remember). Next, that commit on master
must be tagged for easy futurereference to this historical version. Finally, the changes made on the releasebranch need to be merged back into develop
, so that future releases alsocontain these bug fixes.The first two steps in Git:
The release is now done, and tagged for future reference.
Edit: You might as well want to use the
-s
or -u <key>
flags to signyour tag cryptographically.To keep the changes made in the release branch, we need to merge those backinto
develop
, though. In Git:This step may well lead to a merge conflict (probably even, since we havechanged the version number). If so, fix it and commit.
Now we are really done and the release branch may be removed, since we don’tneed it anymore:
Hotfix branches ¶
- May branch off from:
master
- Must merge back into:
develop
andmaster
- Branch naming convention:
hotfix-*
Hotfix branches are very much like release branches in that they are also meantto prepare for a new production release, albeit unplanned. They arise from thenecessity to act immediately upon an undesired state of a live productionversion. When a critical bug in a production version must be resolvedimmediately, a hotfix branch may be branched off from the corresponding tag onthe master branch that marks the production version.
The essence is that work of team members (on the
develop
branch) cancontinue, while another person is preparing a quick production fix.Creating the hotfix branch ¶
Hotfix branches are created from the
master
branch. For example, say version1.2 is the current production release running live and causing troubles due toa severe bug. But changes on develop
are yet unstable. We may then branch offa hotfix branch and start fixing the problem:Don’t forget to bump the version number after branching off!
Then, fix the bug and commit the fix in one or more separate commits.
Finishing a hotfix branch ¶
When finished, the bugfix needs to be merged back into
master
, but also needsto be merged back into develop
, in order to safeguard that the bugfix isincluded in the next release as well. This is completely similar to how releasebranches are finished.First, update
master
and tag the release.Edit: You might as well want to use the
-s
or -u <key>
flags to signyour tag cryptographically.Next, include the bugfix in
develop
, too:The one exception to the rule here is that, when a release branch currentlyexists, the hotfix changes need to be merged into that release branch, insteadof
develop
. Back-merging the bugfix into the release branch will eventuallyresult in the bugfix being merged into develop
too, when the release branchis finished. (If work in develop
immediately requires this bugfix and cannotwait for the release branch to be finished, you may safely merge the bugfixinto develop
now already as well.)Finally, remove the temporary branch:
Summary ¶
While there is nothing really shocking new to this branching model, the “bigpicture” figure that this post began with has turned out to be tremendouslyuseful in our projects. It forms an elegant mental model that is easy tocomprehend and allows team members to develop a shared understanding of thebranching and releasing processes.
A high-quality PDF version of the figure is provided here. Go ahead and hang iton the wall for quick reference at any time.
Update: And for anyone who requested it: here’s thegitflow-model.src.key of the main diagram image (Apple Keynote).
Git-branching-model.pdf
Other posts on this blog
These instructions cover how to get a working copy of the source code and acompiled version of the CPython interpreter (CPython is the version of Pythonavailable from https://www.python.org/). It also gives an overview of thedirectory structure of the CPython source code.
Alternatively, if you have Docker installed youmight want to use our official images. Thesecontain the latest releases of several Python versions, along with git head,and are provided for development and testing purposes only.
See also
The Quick Reference gives brief summary of the process frominstalling git to submitting a pull request.
1.1. Install git
¶
CPython is developed using git for version control. The gitcommand line program is named
git
; this is also used to refer to gititself. git is easily available for all common operating systems.- InstallAs the CPython repo is hosted on GitHub, please refer to either theGitHub setup instructionsor the git project instructions for step-by-stepinstallation directions. You may also want to consider a graphical clientsuch as TortoiseGit orGitHub Desktop.
- ConfigureConfigure your name and email and createan SSH keyas this will allow you to interact with GitHub without typing a usernameand password each time you execute a command, such as
gitpull
,gitpush
, orgitfetch
. On Windows, you should alsoenable autocrlf.
1.2. Get the source code¶
The CPython repo is hosted on GitHub. To get a copy of the source code you shouldfork the Python repository on GitHub, create a localclone of your personal fork, and configure the remotes.
You will only need to execute these steps once: Newsletter expert 2 1. Jixipix photo formation pro 1 0 11 percent.
- Go to https://github.com/python/cpython.
- Press Fork on the top right.
- When asked where to fork the repository, choose to fork it to your username.
- Qr factory 2 9 5 download free. Your fork will be created at
https://github.com/<username>/cpython
. - Clone your GitHub fork (replace
<username>
with your username):(You can use both SSH-based or HTTPS-based URLs.) - Configure an
upstream
remote: - Verify that your setup is correct:
If you did everything correctly, you should now have a copy of the codein the
cpython
directory and two remotes that refer to your own GitHub fork(origin
) and the official CPython repository (upstream
).If you want a working copy of an already-released version of Python,i.e., a version in maintenance mode, you can checkouta release branch. For instance, to checkout a working copy of Python 3.8,do
gitcheckout3.8
.You will need to re-compile CPython when you do such an update.
Do note that CPython will notice that it is being run from a working copy.This means that if you edit CPython’s source code in your working copy,changes to Python code will be picked up by the interpreter for immediateuse and testing. (If you change C code, you will need to recompile theaffected files as described below.)
Patches for the documentation can be made from the same repository; seeDocumenting Python.
1.3. Compile and build¶
CPython provides several compilation flags which help with debugging variousthings. While all of the known flags can be found in the
Misc/SpecialBuilds.txt
file, the most critical one is the Py_DEBUG
flagwhich creates what is known as a “pydebug” build. This flag turns on variousextra sanity checks which help catch common issues. The use of the flag is socommon that turning on the flag is a basic compile option.You should always develop under a pydebug build of CPython (the only instance ofwhen you shouldn’t is if you are taking performance measurements). Even whenworking only on pure Python code the pydebug build provides several usefulchecks that one should not skip.
1.3.1. UNIX¶
The core CPython interpreter only needs a C compiler to be built,however, some of the extension modules will need development headersfor additional libraries (such as the
zlib
library for compression).Depending on what you intend to work on, you might need to install theseadditional requirements so that the compiled interpreter supports thedesired features.If you want to install these optional dependencies, consult theInstall dependencies section below.
If you don’t need to install them, the basic steps for building Pythonfor development is to configure it and then compile it.
Configuration is typically:
More flags are available to
configure
, but this is the minimum you shoulddo to get a pydebug build of CPython.Note
You might need to run
makeclean
before or after re-running configure
in a particular build directory.Once
configure
is done, you can then compile CPython with:This will build CPython with only warnings and errors being printed tostderr and utilize up to 2 CPU cores. If you are using a multi-core machinewith more than 2 cores (or a single-core machine), you can adjust the numberpassed into the
-j
flag to match the number of cores you have (or if yourversion of Make supports it, you can use -j
without a number and Makewill not limit the number of steps that can run simultaneously.).At the end of the build you should see a success message, possibly followedby a list of extension modules that haven’t been built because theirdependencies were missing:
If the build failed and you are using a C89 or C99-compliant compiler,please open a bug report.
If you decide to Install dependencies, you will need to re-run both
configure
and make
.Once CPython is done building you will then have a working buildthat can be run in-place;
./python
on most machines (and what is used inall examples), ./python.exe
wherever a case-insensitive filesystem is used(e.g. on OS X by default), in order to avoid conflicts with the Python
directory. There is normally no need to install your built copyof Python! The interpreter will realize where it is being run fromand thus use the files found in the working copy. If you are worriedyou might accidentally install your working copy build, you can add--prefix=/tmp/python
to the configuration step. When running from yourworking directory, it is best to avoid using the --enable-shared
flagto configure
; unless you are very careful, you may accidentally runwith code from an older, installed shared Python library rather than fromthe interpreter you just built.1.3.1.1. Clang¶
If you are using clang to build CPython, some flags you might want to set toquiet some standard warnings which are specifically superfluous to CPython are
-Wno-unused-value-Wno-empty-body-Qunused-arguments
. You can set yourCFLAGS
environment variable to these flags when running configure
.If you are using clang with ccache, turn off the noisy
parentheses-equality
warnings with the -Wno-parentheses-equality
flag.These warnings are caused by clang not having enough information to detectthat extraneous parentheses in expanded macros are valid, because thepreprocessing is done separately by ccache.If you are using LLVM 2.8, also use the
-no-integrated-as
flag in order tobuild the ctypes
module (without the flag the rest of CPython willstill build properly).1.3.2. Windows¶
For a quick guide to building you can read this documentation from VictorStinner.
Python 3.6 and later can use Microsoft Visual Studio 2017. You can downloadand use any of the free or paid versions of Visual Studio 2017.
When installing Visual Studio 2017, select the Python development workloadand the optional Python native development tools component to obtain all ofthe necessary build tools. If you do not already have git installed, you canfind git for Windows on the Individual components tab of the installer.
Note
If you want to build MSI installers, be aware that the build toolchainfor them has a dependency on the Microsoft .NET Framework Version 3.5 (whichmay not be configured on recent versions of Windows, such as Windows 10). Ifyou are building on a recent Windows version, use the Control Panel (Programs| Programs and Features | Turn Windows Features on or off) and ensure that theentry “.NET Framework 3.5 (includes .NET 2.0 and 3.0)” is enabled.
Your first build should use the command line to ensure any external dependenciesare downloaded:
After this build succeeds, you can open the
PCBuildpcbuild.sln
solution inVisual Studio to continue development.See the readme for more details on what other software is necessary and howto build.
Note
Python 2.7 uses Microsoft Visual Studio 2008, which is most easilyobtained through an MSDN subscription. To use the build files in thePCbuild directory you will also need Visual Studio 2010, see the 2.7readme for more details. If you have VS 2008 but not 2010 you can use thebuild files in the PC/VS9.0 directory, see the VS9 readme for details.
Note
If you are using the Windows Subsystem for Linux (WSL), clone therepository from a native Windows terminal program like cmd.exe command promptor PowerShell as well as use a build of git targeted for Windows, e.g., theofficial one from https://git-scm.com. Otherwise, Visual Studio willnot be able to find all the project’s files and will fail the build.
1.4. Install dependencies¶
This section explains how to install additional extensions (e.g.
zlib
)on Linux and macOs/OS X. On Windows,extensions are already included and built automatically.1.4.1. Linux¶
For UNIX based systems, we try to use system libraries whenever available.This means optional components will only build if the relevant system headersare available. The best way to obtain the appropriate headers will vary bydistribution, but the appropriate commands for some popular distributionsare below.
On Fedora, Red Hat Enterprise Linux and other
yum
based systems:On Fedora and other
DNF
based systems:On Debian, Ubuntu, and other
apt
based systems, try to get thedependencies for the Python you’re working on by using the apt
command.First, make sure you have enabled the source packages in the sources list.You can do this by adding the location of the source packages, includingURL, distribution name and component name, to
/etc/apt/sources.list
.Take Ubuntu Bionic for example:For other distributions, like Debian, change the URL and names to correspondwith the specific distribution.
Then you should update the packages index:
Now you can install the build dependencies via
apt
:If that package is not available for your system, try reducing the minorversion until you find a package that is available.
1.4.2. macOS and OS X¶
For macOS systems (versions 10.12+) and OS X 10.9 and later,the Developer Tools can be downloaded and installed automatically;you do not need to download the complete Xcode application.
If necessary, run the following:
This will also ensure that the system header files are installed into
/usr/include
.On Mac OS X systems (versions 10.0 - 10.7) and OS X 10.8, use the Ccompiler and other development utilities provided by Apple’s Xcode DeveloperTools. The Developer Tools are not shipped with Mac OS X.
For these older releases (versions 10.0 - 10.8), you will need to download either thecorrect version of the Command Line Tools, if available, or install them from thefull Xcode app or package for that OS X release. Older versions may beavailable either as a no-cost download through Apple’s App Store or fromthe Apple Developer web site.
Also note that OS X does not include several libraries used by the Pythonstandard library, including
libzma
, so expect to see some extension modulebuild failures unless you install local copies of them. As of OS X 10.11,Apple no longer provides header files for the deprecated system version ofOpenSSL which means that you will not be able to build the _ssl
extension.One solution is to install these libraries from a third-party packagemanager, like Homebrew or MacPorts, and then add the appropriate pathsfor the header and library files to your configure
command. For example,Gitahead 1 2 – The Easiest Way To Use Git File
with Homebrew:
and
configure
Python versions >= 3.7:or
configure
Python versions < 3.7:and
make
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or MacPorts:
and
configure
:and
make
:There will sometimes be optional modules added for a new release whichwon’t yet be identified in the OS level build dependencies. In those cases,just ask for assistance on the core-mentorship list. If working on bugfixes for Python 2.7, use
python
in place of python3
in the abovecommands.Explaining how to build optional dependencies on a UNIX based system withoutroot access is beyond the scope of this guide.
Note
While you need a C compiler to build CPython, you don’t need anyknowledge of the C language to contribute! Vast areas of CPython arewritten completely in Python: as of this writing, CPython contains slightlymore Python code than C.
1.5. Regenerate configure
¶
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If a change is made to Python which relies on some POSIX system-specificfunctionality (such as using a new system call), it is necessary to update the
configure
script to test for availability of the functionality.Python’s
configure
script is generated from configure.ac
using Autoconf.Instead of editing configure
, edit configure.ac
and then runautoreconf
to regenerate configure
and a number of other files (such aspyconfig.h
).When submitting a patch with changes made to
configure.ac
, you should alsoinclude the generated files.Note that running
autoreconf
is not the same as running autoconf
. Forexample, autoconf
by itself will not regenerate pyconfig.h.in
.autoreconf
runs autoconf
and a number of other tools repeatedly as isappropriate.Python’s
configure.ac
script typically requires a specific version ofAutoconf. At the moment, this reads: AC_PREREQ(2.69)
.If the system copy of Autoconf does not match this version, you will need toinstall your own copy of Autoconf.
1.6. Troubleshoot the build¶
This section lists some of the common problems that may arise during thecompilation of Python, with proposed solutions.
1.6.1. Avoid recreating auto-generated files¶
Under some circumstances you may encounter Python errors in scripts like
Parser/asdl_c.py
or Python/makeopcodetargets.py
while running make
.Python auto-generates some of its own code, and a full build from scratch needsto run the auto-generation scripts. However, this makes the Python build requirean already installed Python interpreter; this can also cause version mismatcheswhen trying to build an old (2.x) Python with a new (3.x) Python installed, orvice versa.To overcome this problem, auto-generated files are also checked into theGit repository. So if you don’t touch the auto-generation scripts, there’sno real need to auto-generate anything.
1.7. Editors and Tools¶
Python is used widely enough that practically all code editors have some formof support for writing Python code. Various coding tools also include Pythonsupport.
For editors and tools which the core developers have felt some special commentis needed for coding in Python, see Additional Resources.
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1.8. Directory structure¶
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There are several top-level directories in the CPython source tree. Knowing whateach one is meant to hold will help you find where a certain piece offunctionality is implemented. Do realize, though, there are always exceptions toevery rule.
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Doc
- The official documentation. This is what https://docs.python.org/ uses.See also Building the documentation.
Grammar
- Contains the EBNF grammar file forPython.
Include
- Contains all interpreter-wide header files.
Lib
- The part of the standard library implemented in pure Python.
Mac
- Mac-specific code (e.g., using IDLE as an OS X application).
Misc
- Things that do not belong elsewhere. Typically this is varying kinds ofdeveloper-specific documentation.
Modules
- The part of the standard library (plus some other code) that is implementedin C.
Objects
- Code for all built-in types.
PC
- Windows-specific code.
PCbuild
- Build files for the version of MSVC currently used for the Windowsinstallers provided on python.org.
Parser
- Code related to the parser. The definition of the AST nodes is also kepthere.
Programs
- Source code for C executables, including the main function for theCPython interpreter (in versions prior to Python 3.5, these files arein the Modules directory).
Python
- The code that makes up the core CPython runtime. This includes thecompiler, eval loop and various built-in modules.
Tools
- Various tools that are (or have been) used to maintain Python.