版本管理 命名有意义的版本号2.0.0-rc1

laofo · 2013年06月19日 · 14 次阅读

作者:yaoxing 转自:http://www.cnblogs.com/yaoxing/archive/2012/05/14/semantic-versioning.html

在软件管理的世界里有一个可怕的地方叫 “依赖地狱 (dependency hell)”。你的系统越是成长壮大,你越是整合更多的软件包到你自己的系统中,你越有可能在将来的某天发现自己已经掉进了这个绝望的深渊。

在一个有着众多依赖的系统里,发布新版本可能很快成为一个恶梦。如果依赖定义得过于紧密,你就有可能进入版本锁定 (version lock) 的状态(版本锁定是指一旦更新一个软件包,就不得不更新其他所有依赖于它的包)。如果依赖定义得过于松散,你又难免会被版本穿插 (version promiscuity) 所伤(让人以为会与多得不合理的未来版本兼容)。当你被版本锁定或版本穿插所阻挠而不能容易地让你的项目顺利前进时,你就身处依赖地狱中了。

作为这个问题的解决方案之一,我提议用一组简单的规则和要求来约束版本号的分配和增长规则。为了让这套理论运作,你必须预先定义好自己的公共 API。这可以通过文档定义或代码强制要求来实现。无论如何,这套 API 的清楚明了是十分重要的。一旦你定义了公共 API,你就可以通过修改相应的版本号来通知大家你的修改。考虑使用这样的版本号格式:X.Y.Z(主版本号,次版本号,补丁版本号)修复 Bug 但不影响 API 时增长补丁版本号;API 保持向下兼容的增加/修改时增长次版本号;进行不向下兼容的修改时增长主版本号。

我把这套规则称为 “语义版本命名 (Semantic Versioning)”。在这套工作模式下,版本号和它们的增长模式就会传达从当前版本向下一个版本进行了怎样的修改。

语义版本 (SemVer) 命名规范 在篇文章里出现的关键字 “必须”,“必须不”,“要求”,“应该”,“不应该”,“一定要”,“一定不要”,“推荐”,“可以” 和 “可选” 将在 RFC2119 中描述和解释。(以下译文中原样使用这些关键字看上去会比较生硬,但为了清楚地传达作者的意图和保持 RFC2119 关键字的意义,仍然照这里的翻译来使用——译者注)

使用语义版本命名的软件系统必须定义一套公共 API。这套 API 可以是在代码中申明或是用严格的文档定义。不管怎样做,它都应该清楚明了。 正常的版本号必须使用 X.Y.Z 的形式并且 X/Y/Z 是非负整数。X 是主版本号,Y 是次版本号,Z 是补丁版本号。版本号每次必须只能增长 1。例如:1.9.0->1.10.0->1.11.0。 当主版本号增长时,次版本号和补丁版本号必须清零。当次版本号增长时,补丁版本号必须清零。例如:1.1.9->2.0.0,2.1.7->2.2.0。 一旦发布了具有版本的包,那个版本的内容必须不能再更改。任何修改必须发布成一个新版本。 主版本号 0 (0.y.z) 是用来进行初始开发时使用的。任何东西都可能在任何时候改变。公共 API 此时应该被认为是经常变动的。 版本 1.0.0 开始定义公共 API。这个版本及以后的版本号的增长方式将依赖于公共 API 以及它如何变化。 如果有任何向下兼容的 bug 修复发生,补丁版本号 Z (x.y.Z | x > 0) 必须增长 1。“bug 修复” 被定义为内部进行的修复非正常行为的修复工作。 如果进行了新的并且向下兼容的公共 API 添加和修改,次版本号 Y (x.Y.z | x > 0) 必须增长 1。如果任何公共 API 被标记为 “过期”,次版本号必须增长 1;如果有大量的新功能或改进在内部代码中发生,次版本号可以增长 1;这其中也可以包含补丁级别的修改。当次版本号增长时补丁版本号必须清零。 如果对公共 API 有任何向下不兼容的修改,主版本号 X (X.y.z | X > 0) 必须增长 1。这其中也可以包含次版本和补丁版本级别的修改。当主版本号增长时次版本号和补丁版本号必须清零。 预览版本(pre-release version)可以通过在补丁版本号后追加中横线以及由点分隔开的一系列标识来表达。标识必须由 ASCII 字符和中横线 [0-9A-Za-z-] 组成。预览版本能满足相关版本的要求,但优先级低于相关版本。例如:1.0.0-alpha,1.0.0-alpha.2,1.0.0-0.3.7,1.0.0-x.7.z.92。 构建版本(build version)可以通过在补丁版本号或预览版本后追加一个加号和一系列由点分隔标识来表达。标识必须由 ASCII 字符和中横线 [0-9A-Za-z-] 组成。构建版本能够满足相关版本的要求,并且优先于相关版本。例如:1.0.0+build.1,1.3.7+build.11.e0f985a。 将版本号分为主版本号、次版本号、补丁版本号,预览版本,构建版本,必须按这样的按顺序分别逐级考虑来确定版本顺序。主版本号、次版本号,补丁版本号总是通过数字大小来确定顺序。预览版本和构建版本的顺序必须由比较由点分隔标识来确定,规则如下:如果标识只有数字,则由数字大小决定;如果标识包含字符和中横线,则由比较字符的字典顺序来确定。数字标识的顺序永远低于非数字标识。例如:1.0.0-alpha < 1.0.0-alpha.1 < 1.0.0-beta.2 < 1.0.0-beta.11 < 1.0.0-rc.1 < 1.0.0-rc.1+build.1 < 1.0.0 < 1.0.0+0.3.7 < 1.3.7+build < 1.3.7+build.2.b8f12d7 < 1.3.7+build.11.e0f985a。 为什么使用语义版本命名? 这并不是一个全新的革命性的想法。事实上,你可能已经做了和这差不多的事情了。问题是 “差不多” 还不够好。如果不服从某种正式的规范,版本号对于版本依赖管理就失去了本质上的意义。通过给以上的想法一个清楚的定义和命名,与你的软件用户沟通你的意图就变得容易了。一旦这些意图明确表达出来,灵活(但不是过于灵活)的依赖定义就可以最终被制定出来。

一个简单的例子可以演示语义版本命名如何让版本地狱成为过去。考虑有一个库叫做 “救火车”。它需要一个语义版本命名的包 “云梯”。当救火车被制造的时候,云梯的版本是 3.1.0。因为救火车一开始使用了由云梯 3.1.0 提供的某些功能,你可以安全地知道对云梯的正确依赖是在 3.1.0 以后并且 4.0.0 之前。现在,当云梯版本 3.1.1 和 3.2.0 发布时,你就可以把它们放到你的软件包管理系统中并且知道它们会与依赖它的软件兼容。

作为一个有责任的开发人员,你当然一定会想要确保所有软件包更新都被广而告之。现实世界是一个混乱的地方,除了提高警惕我们别无他法。你所能做的是让语义版本命名为你提供一个健全的方式来发布版本更新软件包,而不必更新所有的依赖软件包,这将会节省你的时间,少为你添麻烦。

如果这些听起来让你满意的话,你所需要对语义版本命名做的事情就是:申明你正在使用它并且按它的要求办事。在你的 README 文档中链接到这个网站,让其他人知道这些规则并且从中受益。

FAQ 【内容太多,过两天再补】

关于 语义版本命名规范由 Tom Preston-Werner 提出,他是 Gravatars 的创始人和 GitHub 的合作创始人。

如果你想留下一些反馈,请在 GitHub 提交一个新的问题。

License Creative Commons - CC BY 3.0 http://creativecommons.org/licenses/by/3.0/

简单说

英文原文在这里

原文地址:http://semver.org/

Semantic Versioning 2.0.0

Summary

Given a version number MAJOR.MINOR.PATCH, increment the:

MAJOR version when you make incompatible API changes, MINOR version when you add functionality in a backwards-compatible manner, and PATCH version when you make backwards-compatible bug fixes. Additional labels for pre-release and build metadata are available as extensions to the MAJOR.MINOR.PATCH format.

Introduction

In the world of software management there exists a dread place called "dependency hell." The bigger your system grows and the more packages you integrate into your software, the more likely you are to find yourself, one day, in this pit of despair.

In systems with many dependencies, releasing new package versions can quickly become a nightmare. If the dependency specifications are too tight, you are in danger of version lock (the inability to upgrade a package without having to release new versions of every dependent package). If dependencies are specified too loosely, you will inevitably be bitten by version promiscuity (assuming compatibility with more future versions than is reasonable). Dependency hell is where you are when version lock and/or version promiscuity prevent you from easily and safely moving your project forward.

As a solution to this problem, I propose a simple set of rules and requirements that dictate how version numbers are assigned and incremented. These rules are based on but not necessarily limited to pre-existing widespread common practices in use in both closed and open-source software. For this system to work, you first need to declare a public API. This may consist of documentation or be enforced by the code itself. Regardless, it is important that this API be clear and precise. Once you identify your public API, you communicate changes to it with specific increments to your version number. Consider a version format of X.Y.Z (Major.Minor.Patch). Bug fixes not affecting the API increment the patch version, backwards compatible API additions/changes increment the minor version, and backwards incompatible API changes increment the major version.

I call this system "Semantic Versioning." Under this scheme, version numbers and the way they change convey meaning about the underlying code and what has been modified from one version to the next.

Semantic Versioning Specification (SemVer)

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

Software using Semantic Versioning MUST declare a public API. This API could be declared in the code itself or exist strictly in documentation. However it is done, it should be precise and comprehensive.

A normal version number MUST take the form X.Y.Z where X, Y, and Z are non-negative integers, and MUST NOT contain leading zeroes. X is the major version, Y is the minor version, and Z is the patch version. Each element MUST increase numerically. For instance: 1.9.0 -> 1.10.0 -> 1.11.0.

Once a versioned package has been released, the contents of that version MUST NOT be modified. Any modifications MUST be released as a new version.

Major version zero (0.y.z) is for initial development. Anything may change at any time. The public API should not be considered stable.

Version 1.0.0 defines the public API. The way in which the version number is incremented after this release is dependent on this public API and how it changes.

Patch version Z (x.y.Z | x > 0) MUST be incremented if only backwards compatible bug fixes are introduced. A bug fix is defined as an internal change that fixes incorrect behavior.

Minor version Y (x.Y.z | x > 0) MUST be incremented if new, backwards compatible functionality is introduced to the public API. It MUST be incremented if any public API functionality is marked as deprecated. It MAY be incremented if substantial new functionality or improvements are introduced within the private code. It MAY include patch level changes. Patch version MUST be reset to 0 when minor version is incremented.

Major version X (X.y.z | X > 0) MUST be incremented if any backwards incompatible changes are introduced to the public API. It MAY include minor and patch level changes. Patch and minor version MUST be reset to 0 when major version is incremented.

A pre-release version MAY be denoted by appending a hyphen and a series of dot separated identifiers immediately following the patch version. Identifiers MUST comprise only ASCII alphanumerics and hyphen [0-9A-Za-z-]. Identifiers MUST NOT be empty. Numeric identifiers MUST NOT include leading zeroes. Pre-release versions have a lower precedence than the associated normal version. A pre-release version indicates that the version is unstable and might not satisfy the intended compatibility requirements as denoted by its associated normal version. Examples: 1.0.0-alpha, 1.0.0-alpha.1, 1.0.0-0.3.7, 1.0.0-x.7.z.92.

Build metadata MAY be denoted by appending a plus sign and a series of dot separated identifiers immediately following the patch or pre-release version. Identifiers MUST comprise only ASCII alphanumerics and hyphen [0-9A-Za-z-]. Identifiers MUST NOT be empty. Build metadata SHOULD be ignored when determining version precedence. Thus two versions that differ only in the build metadata, have the same precedence. Examples: 1.0.0-alpha+001, 1.0.0+20130313144700, 1.0.0-beta+exp.sha.5114f85.

Precedence refers to how versions are compared to each other when ordered. Precedence MUST be calculated by separating the version into major, minor, patch and pre-release identifiers in that order (Build metadata does not figure into precedence). Precedence is determined by the first difference when comparing each of these identifiers from left to right as follows: Major, minor, and patch versions are always compared numerically. Example: 1.0.0 < 2.0.0 < 2.1.0 < 2.1.1. When major, minor, and patch are equal, a pre-release version has lower precedence than a normal version. Example: 1.0.0-alpha < 1.0.0. Precedence for two pre-release versions with the same major, minor, and patch version MUST be determined by comparing each dot separated identifier from left to right until a difference is found as follows: identifiers consisting of only digits are compared numerically and identifiers with letters or hyphens are compared lexically in ASCII sort order. Numeric identifiers always have lower precedence than non-numeric identifiers. A larger set of pre-release fields has a higher precedence than a smaller set, if all of the preceding identifiers are equal. Example: 1.0.0-alpha < 1.0.0-alpha.1 < 1.0.0-alpha.beta < 1.0.0-beta < 1.0.0-beta.2 < 1.0.0-beta.11 < 1.0.0-rc.1 < 1.0.0.

Why Use Semantic Versioning?

This is not a new or revolutionary idea. In fact, you probably do something close to this already. The problem is that "close" isn't good enough. Without compliance to some sort of formal specification, version numbers are essentially useless for dependency management. By giving a name and clear definition to the above ideas, it becomes easy to communicate your intentions to the users of your software. Once these intentions are clear, flexible (but not too flexible) dependency specifications can finally be made.

A simple example will demonstrate how Semantic Versioning can make dependency hell a thing of the past. Consider a library called "Firetruck." It requires a Semantically Versioned package named "Ladder." At the time that Firetruck is created, Ladder is at version 3.1.0. Since Firetruck uses some functionality that was first introduced in 3.1.0, you can safely specify the Ladder dependency as greater than or equal to 3.1.0 but less than 4.0.0. Now, when Ladder version 3.1.1 and 3.2.0 become available, you can release them to your package management system and know that they will be compatible with existing dependent software.

As a responsible developer you will, of course, want to verify that any package upgrades function as advertised. The real world is a messy place; there's nothing we can do about that but be vigilant. What you can do is let Semantic Versioning provide you with a sane way to release and upgrade packages without having to roll new versions of dependent packages, saving you time and hassle.

If all of this sounds desirable, all you need to do to start using Semantic Versioning is to declare that you are doing so and then follow the rules. Link to this website from your README so others know the rules and can benefit from them.

FAQ

How should I deal with revisions in the 0.y.z initial development phase?

The simplest thing to do is start your initial development release at 0.1.0 and then increment the minor version for each subsequent release.

How do I know when to release 1.0.0?

If your software is being used in production, it should probably already be 1.0.0. If you have a stable API on which users have come to depend, you should be 1.0.0. If you're worrying a lot about backwards compatibility, you should probably already be 1.0.0.

Doesn't this discourage rapid development and fast iteration?

Major version zero is all about rapid development. If you're changing the API every day you should either still be in version 0.y.z or on a separate development branch working on the next major version.

If even the tiniest backwards incompatible changes to the public API require a major version bump, won't I end up at version 42.0.0 very rapidly?

This is a question of responsible development and foresight. Incompatible changes should not be introduced lightly to software that has a lot of dependent code. The cost that must be incurred to upgrade can be significant. Having to bump major versions to release incompatible changes means you'll think through the impact of your changes, and evaluate the cost/benefit ratio involved.

Documenting the entire public API is too much work!

It is your responsibility as a professional developer to properly document software that is intended for use by others. Managing software complexity is a hugely important part of keeping a project efficient, and that's hard to do if nobody knows how to use your software, or what methods are safe to call. In the long run, Semantic Versioning, and the insistence on a well defined public API can keep everyone and everything running smoothly.

What do I do if I accidentally release a backwards incompatible change as a minor version?

As soon as you realize that you've broken the Semantic Versioning spec, fix the problem and release a new minor version that corrects the problem and restores backwards compatibility. Even under this circumstance, it is unacceptable to modify versioned releases. If it's appropriate, document the offending version and inform your users of the problem so that they are aware of the offending version.

What should I do if I update my own dependencies without changing the public API?

That would be considered compatible since it does not affect the public API. Software that explicitly depends on the same dependencies as your package should have their own dependency specifications and the author will notice any conflicts. Determining whether the change is a patch level or minor level modification depends on whether you updated your dependencies in order to fix a bug or introduce new functionality. I would usually expect additional code for the latter instance, in which case it's obviously a minor level increment.

What if I inadvertently alter the public API in a way that is not compliant with the version number change (i.e. the code incorrectly introduces a major breaking change in a patch release)

Use your best judgment. If you have a huge audience that will be drastically impacted by changing the behavior back to what the public API intended, then it may be best to perform a major version release, even though the fix could strictly be considered a patch release. Remember, Semantic Versioning is all about conveying meaning by how the version number changes. If these changes are important to your users, use the version number to inform them.

How should I handle deprecating functionality?

Deprecating existing functionality is a normal part of software development and is often required to make forward progress. When you deprecate part of your public API, you should do two things: (1) update your documentation to let users know about the change, (2) issue a new minor release with the deprecation in place. Before you completely remove the functionality in a new major release there should be at least one minor release that contains the deprecation so that users can smoothly transition to the new API.

Does semver have a size limit on the version string?

No, but use good judgment. A 255 character version string is probably overkill, for example. Also, specific systems may impose their own limits on the size of the string.

About

The Semantic Versioning specification is authored by Tom Preston-Werner, inventor of Gravatars and cofounder of GitHub.

If you'd like to leave feedback, please open an issue on GitHub.

License

Creative Commons - CC BY 3.0 http://creativecommons.org/licenses/by/3.0/

您好!请问这个 API 是指什么?

如果按照需求功能模块来定义版本的递增,那产品和实施的版本怎么定义?

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