我不太确定“标签”是什么，但分支是一个相当常见的源代码控制概念。

基本上，分支是在不影响主干的情况下对代码进行更改的一种方式。假设您想要添加一个相当复杂的新功能。您希望能够在进行更改时检入更改，但在完成该特性之前不希望它影响trunk。

首先创建一个分支。这基本上是创建分支时的主干副本。然后在分支中完成所有工作。在分支中所做的任何更改都不会影响trunk，因此trunk仍然可用，允许其他人继续在那里工作(比如做错误修复或小的增强)。一旦你的特性完成了，你就可以把分支集成回主干中。这将把所有的更改从分支移动到主干。

人们为分支使用了许多模式。如果您有一个同时支持多个主要版本的产品，通常每个版本都是一个分支。在我工作的地方，我们有一个QA分支和一个生产分支。在向QA发布代码之前，我们将变更集成到QA分支，然后从那里进行部署。当发布到产品时，我们从QA分支集成到生产分支，所以我们知道在生产中运行的代码与QA测试的代码是相同的。

这里是维基百科上关于分支的条目，因为它们可能比我能更好地解释事情。：）

对于熟悉GIT的人来说，GIT中的master相当于SVN中的trunk。

分支和标记在GIT和SVN中有相同的术语。

嗯，我不确定我同意尼克重新标签类似于一个分支。标签只是一个标记

Trunk would be the main body of development, originating from the start of the project until the present. Branch will be a copy of code derived from a certain point in the trunk that is used for applying major changes to the code while preserving the integrity of the code in the trunk. If the major changes work according to plan, they are usually merged back into the trunk. Tag will be a point in time on the trunk or a branch that you wish to preserve. The two main reasons for preservation would be that either this is a major release of the software, whether alpha, beta, RC or RTM, or this is the most stable point of the software before major revisions on the trunk were applied.

在开源项目中，不被项目涉众接受的主要分支可以成为分叉的基础——例如，与其他源代码共享共同起源的完全独立的项目。

分支和标记子树与主干的区别如下:

Subversion allows sysadmins to create hook scripts which are triggered for execution when certain events occur; for instance, committing a change to the repository. It is very common for a typical Subversion repository implementation to treat any path containing "/tag/" to be write-protected after creation; the net result is that tags, once created, are immutable (at least to "ordinary" users). This is done via the hook scripts, which enforce the immutability by preventing further changes if tag is a parent node of the changed object.

Subversion从1.5版开始还增加了与“分支合并跟踪”相关的特性，这样提交到分支的更改就可以合并回支持增量式“智能”合并的主干中。

除了Nick所说的，您还可以在流式线:并行软件开发的分支模式中找到更多信息

在这个图中，main是主干，rel1- maintenance是分支，1.0是标记。

一般来说(工具不可知的观点)，分支是用于并行开发的机制。一个SCM可以有0到n个分支。Subversion是0。

Trunk is a main branch recommended by Subversion, but you are in no way forced to create it. You could call it 'main' or 'releases', or not have one at all! Branch represents a development effort. It should never be named after a resource (like 'vonc_branch') but after: a purpose 'myProject_dev' or 'myProject_Merge' a release perimeter 'myProjetc1.0_dev'or myProject2.3_Merge' or 'myProject6..2_Patch1'... Tag is a snapshot of files in order to easily get back to that state. The problem is that tag and branch is the same in Subversion. And I would definitely recommend the paranoid approach: you can use one of the access control scripts provided with Subversion to prevent anyone from doing anything but creating new copies in the tags area.

标签是最终的。其内容不应改变。从来没有。永远。你忘了发行通知里的一行字?创建一个新标记。淘汰或删除旧的。

现在，我读了很多关于“在某某分支中合并某某，然后最终在主干分支中合并”的内容。 这就是所谓的合并工作流，这里没有强制性的内容。这并不是因为你有一个主干分支，你必须合并回任何东西。

按照惯例，主干分支可以代表您的开发的当前状态，但这是一个简单的顺序项目，该项目具有:

没有“预先”开发(用于准备下一个下一个版本，这意味着这些更改与当前的“主干”开发不兼容) 没有大规模的重构(用于测试新的技术选择) 没有以前版本的长期维护

因为对于这些场景中的一个(或所有)，你会得到四个“主干”，四个“当前开发”，而不是你在这些并行开发中所做的所有事情都必须合并回“主干”中。

当我在OpenCV 2计算机视觉应用编程烹饪书的作者的网站上查找时，我发现了这个关于SVN的很棒的教程，我想我应该分享一下。

他有一个关于如何使用SVN的教程，以及短语“trunk”、“tag”和“branch”的含义。

直接引用自他的教程:

The current version of your software project, on which your team is currently working is usually located under a directory called trunk. As the project evolves, the developer updates that version fix bugs, add new features) and submit his changes under that directory. At any given point in time, you may want to freeze a version and capture a snapshot of the software as it is at this stage of the development. This generally corresponds to the official versions of your software, for example, the ones you will deliver to your clients. These snapshots are located under the tags directory of your project. Finally, it is often useful to create, at some point, a new line of development for your software. This happens, for example, when you wish to test an alternative implementation in which you have to modify your software but you do not want to submit these changes to the main project until you decide if you adopt the new solution. The main team can then continue to work on the project while other developer work on the prototype. You would put these new lines of development of the project under a directory called branches.