What is Git
By far, the most widely used modern version control system in the world today is Git. Git is a mature, actively maintained open source project originally developed in 2005 by Linus Torvalds, the famous creator of the Linux operating system kernel. A staggering number of software projects rely on Git for version control, including commercial projects as well as open source. Developers who have worked with Git are well represented in the pool of available software development talent and it works well on a wide range of operating systems and IDEs (Integrated Development Environments).
Having a distributed architecture, Git is an example of a DVCS (hence Distributed Version Control System). Rather than have only one single place for the full version history of the software as is common in once-popular version control systems like CVS or Subversion (also known as SVN), in Git, every developer's working copy of the code is also a repository that can contain the full history of all changes.
In addition to being distributed, Git has been designed with performance, security and flexibility in mind.
The raw performance characteristics of Git are very strong when compared to many alternatives. Committing new changes, branching, merging and comparing past versions are all optimized for performance. The algorithms implemented inside Git take advantage of deep knowledge about common attributes of real source code file trees, how they are usually modified over time and what the access patterns are.
Unlike some version control software, Git is not fooled by the names of the files when determining what the storage and version history of the file tree should be, instead, Git focuses on the file content itself. After all, source code files are frequently renamed, split, and rearranged. The object format of Git's repository files uses a combination of delta encoding (storing content differences), compression and explicitly stores directory contents and version metadata objects.
Being distributed enables significant performance benefits as well.
For example, say a developer, Alice, makes changes to source code, adding a feature for the upcoming 2.0 release, then commits those changes with descriptive messages. She then works on a second feature and commits those changes too. Naturally these are stored as separate pieces of work in the version history. Alice then switches to the version 1.3 branch of the same software to fix a bug that affects only that older version. The purpose of this is to enable Alice's team to ship a bug fix release, version 1.3.1, before version 2.0 is ready. Alice can then return to the 2.0 branch to continue working on new features for 2.0 and all of this can occur without any network access and is therefore fast and reliable. She could even do it on an airplane. When she is ready to send all of the individually committed changes to the remote repository, Alice can "push" them in one command.
Git has been designed with the integrity of managed source code as a top priority. The content of the files as well as the true relationships between files and directories, versions, tags and commits, all of these objects in the Git repository are secured with a cryptographically secure hashing algorithm called SHA1. This protects the code and the change history against both accidental and malicious change and ensures that the history is fully traceable.
With Git, you can be sure you have an authentic content history of your source code.
Some other version control systems have no protections against secret alteration at a later date. This can be a serious information security vulnerability for any organization that relies on software development.
One of Git's key design objectives is flexibility. Git is flexible in several respects: in support for various kinds of nonlinear development workflows, in its efficiency in both small and large projects and in its compatibility with many existing systems and protocols.
Git has been designed to support branching and tagging as first-class citizens (unlike SVN) and operations that affect branches and tags (such as merging or reverting) are also stored as part of the change history. Not all version control systems feature this level of tracking.
使用 Git 进行版本控制
Git is the best choice for most software teams today. While every team is different and should do their own analysis, here are the main reasons why version control with Git is preferred over alternatives:
Git is good
Git has the functionality, performance, security and flexibility that most teams and individual developers need. These attributes of Git are detailed above. In side-by-side comparisons with most other alternatives, many teams find that Git is very favorable.
Git is a de facto standard
Git is the most broadly adopted tool of its kind. This is makes Git attractive for the following reasons. At Atlassian, nearly all of our project source code is managed in Git.
Vast numbers of developers already have Git experience and a significant proportion of college graduates may have experience with only Git. While some organizations may need to climb the learning curve when migrating to Git from another version control system, many of their existing and future developers do not need to be trained on Git.
In addition to the benefits of a large talent pool, the predominance of Git also means that many third party software tools and services are already integrated with Git including IDEs, and our own tools like DVCS desktop client Sourcetree, issue and project tracking software, Jira, and code hosting service, Bitbucket.
If you are an inexperienced developer wanting to build up valuable skills in software development tools, when it comes to version control, Git should be on your list.
Git is a quality open source project
Git is a very well supported open source project with over a decade of solid stewardship. The project maintainers have shown balanced judgment and a mature approach to meeting the long term needs of its users with regular releases that improve usability and functionality. The quality of the open source software is easily scrutinized and countless businesses rely heavily on that quality.
Git enjoys great community support and a vast user base. Documentation is excellent and plentiful, including books, tutorials and dedicated web sites. There are also podcasts and video tutorials.
Being open source lowers the cost for hobbyist developers as they can use Git without paying a fee. For use in open-source projects, Git is undoubtedly the successor to the previous generations of successful open source version control systems, SVN and CVS.
Criticism of Git
One common criticism of Git is that it can be difficult to learn. Some of the terminology in Git will be novel to newcomers and for users of other systems, the Git terminology may be different, for example,
revert in Git has a different meaning than in SVN or CVS. Nevertheless, Git is very capable and provides a lot of power to its users. Learning to use that power can take some time, however once it has been learned, that power can be used by the team to increase their development speed.
For those teams coming from a non-distributed VCS, having a central repository may seem like a good thing that they don't want to lose. However, while Git has been designed as a distributed version control system (DVCS), with Git, you can still have an official, canonical repository where all changes to the software must be stored. With Git, because each developer's repository is complete, their work doesn't need to be constrained by the availability and performance of the "central" server. During outages or while offline, developers can still consult the full project history. Because Git is flexible as well as being distributed, you can work the way you are accustomed to but gain the additional benefits of Git, some of which you may not even realise you're missing.
Now that you understand what version control is, what Git is and why software teams should use it, read on to discover the benefits Git can provide across the whole organization.