SVN Team Provider

This proposal has been withdrawn.

Introduction

The SVN Team Provider Project is a proposed open source project under the Eclipse Technology Project.

This proposal is in the Project Proposal Phase (as defined in the Eclipse Development Process document) and is written to declare its intent and scope. This proposal is written to solicit additional participation and input from the Eclipse community. You are invited to comment on and/or join the project. Please send all feedback to the http://www.eclipse.org/newsportal/thread.php?group=eclipse.technology.svn newsgroup.

Background

Subversion (SVN) is very popular and rivals CVS as the most widely used open source version control system. Many hosting services are providing SVN access, and several major open source projects have converted their CVS repositories to SVN. Eclipse has great support for CVS, and users are looking for similar support for SVN. Eclipse has no support for SVN out of the box and many new users are unaware that quality third-party SVN team providers are available. This perceived lack of SVN support makes Eclipse look inferior to other IDEs such as Netbeans and IntelliJ that ship with SVN support in their base installations. The Bugzilla entry to add SVN support to Eclipse, #37154, has over 100 votes and has been in the top-5 for most votes for a very long time.

In addition to adding SVN support to Eclipse, there is the issue of providing a solid Team API that can be leveraged by commercial and open source SCM providers. The current Team API is very capable, but at the same time it is also hindered by having only one concrete implementation. In many instances the API has become very CVS-centric. Having the platform support a second team provider would provide further validation of Team APIs before they are released and consumed by other team providers.

Finally, there is the issue of providing support for SVN to projects hosted by Eclipse.org. The code for this project should be self-hosted in an SVN repository and it is likely that there are other projects currently hosted at Eclipse.org that would like to change their repositories from CVS to SVN. For reference purposes, there are existing Bugzilla entries to add support for hosting projects in Subversion repositories (see #71735 and #131096). Part of this proposal is to provide resources and expertise that will support the Eclipse Foundation in their efforts to provide these services to the community. There are many individuals involved in the Subclipse community, and the wider Subversion ecosystem, who would be willing to volunteer time towards assisting the Eclipse organization on setting up its own Subversion repository, as a complement to its existing CVS repository. There are also commercial entities in the Subversion ecosystem, and some Eclipse members, who could offer commercial assistance on this regard.

History

One of the main problems with CVS that Subversion sought to address was the lack of an official API. Subversion was designed as a set of layered libraries with well-defined interfaces, designed to be called by other applications. These libraries are delivered as native C libraries in order to achieve the maximum portability across both operating systems and programming languages, as most languages have a facility for accessing C libraries. JavaHL is the name for the official Java language binding to these libraries. JavaHL is similar to SWT in that it accesses the native libraries via JNI while providing a standardized interface to Java clients. Since virtually all SVN clients use these same libraries, there is great compatibility when using multiple clients on the same local working copy. The Subversion API also has very strictly defined compatibility rules and the Subversion client and server are both forward and backward compatible with each other.

The Subclipse project has figured out how to deliver the native libraries for JavaHL for the Windows platform only. Currently, an Eclipse user running on Linux has to install Subversion using the packaging system for their distribution. This then installs all of the required native libraries, including the JavaHL library. There are similar facilities available for OS X users. We would be interested in working with the Eclipse platform project to see if there are changes that could be made to Eclipse to enable native libraries to be delivered by a plug-in fragment when those libraries have dependencies on other libraries. In the short term, users on non-Windows platforms would have to obtain the JavaHL native library for their operating system. All of the major Linux distributions now make this very easy to do and really it is not much different than how a Linux user that uses KDE has to make sure they have the GTK2 libraries installed before they can use SWT and Eclipse.

There is also a third-party library named JavaSVN that has been developed by a company named TMate. http://tmate.org/svn/. They have reverse-engineered the SVN network protocols and working copy format and have produced a 100% pure Java implementation of the JavaHL interface; making it a drop in replacement for the native library version of JavaHL. The Subclipse distribution currently provides an adapter option for this library. The JavaSVN library license is not compatible with the EPL, so we will not provide this library or its adapter as part of the project. We will work with TMate to assist them in providing a plug-in that is downloadable via their web site that adds JavaSVN as an adapter option via our public extension point. This has always been the option that TMate has expressed as their preference, and they have asked to be listed as both a supporter and interested party of this project. External packagers of Eclipse plug-ins, such as Linux distributions (Fedora, Debian) and/or Yoxos would likely be able to include JavaSVN in their distributions as the JavaSVN license would be compatible with what they are doing.

In the process of putting together this proposal, as well as in prior related discussions, we have received a lot of feedback about the issue of using native libraries (JavaHL). It is our position that using the native libraries provided by Subversion is the right approach to take. The existing CVS plug-in took the approach of creating a custom pure Java library. However, it needs to be taken into account that:

  1. There really was/is no official CVS "API" that could have been used.
  2. CVS development was already largely dormant before Eclipse development even started.

Despite this second point, even to this day there is still the occasional incompatibility between the Eclipse CVS client and other CVS clients or servers. Subversion, in contrast to CVS, has an official API that was designed to be used by multiple languages, including Java, and more importantly Subversion is actively developed and frequently sees major new features being added. It would be a mistake to think that all of the work that has gone into Subversion, and continues to go into it to this day could be easily replicated and managed. It would be better for Eclipse, as a platform for application development, to put this effort into making it easier to use native libraries in Eclipse plug-ins and applications. Surely any problems in this area are solvable, and Eclipse would just be that much better if it did solve those problems.

Scope

The objectives of the SVN Team Provider project are to:

  • Provide support for accessing and manipulating projects that are hosted in a Subversion repository.
  • Provide UI and features that are familiar to existing Eclipse CVS users, while at the same time providing an appropriate user interface for accessing Subversion specific features.
  • Provide a simple API for accessing Subversion functions, as well as support headless operations of Team provider functions. These items will make it easier for other plug-ins to add Subversion functionality as needed.
  • Provide accurate and up to date documentation on using the features of the SVN provider.
  • Support, implement and follow the latest best practices for Eclipse UI development as appropriate for the current Eclipse release.
  • Contribute to the development and refinement of the Eclipse Core Team API.
  • Provide real world use cases for development of the official JavaHL SVN client interface.
  • Assist resources at the Eclipse Foundation in offering SVN hosting to projects.
  • Assist the release engineering team to add SVN support to their tools and process.

Description

The initial code for this project will be based on a code contribution from the Subclipse project. Subclipse was recently re-licensed under the terms of the EPL and provides a robust and stable implementation of Subversion functionality as an Eclipse Team Provider. In addition, this project will adhere to common Eclipse development best practices, most of which are already in place in the Subclipse code base.

  • Separation into core and ui plug-ins.
  • JUnit test suite.
  • Internal packages for non-public API.
  • Export and use of extension points.
  • Separate help plugin for documentation as well as use of context sensitive help.
  • Localization support. The Subclipse community has contributed localizations for Japanese (ja), Chinese (zh), and Traditional Chinese (zh_TW).

The Subclipse code and architecture is based on the Eclipse CVS provider, so it should be easy for the existing Team and CVS developers to understand, should they decide to contribute.

The foundation for this project is a common Subversion API layer called the SVN Client Adapter (org.eclipse.subversion.client). This adapter gives clients full access to any SVN repository (even those not under direct control of the SVN Team Provider). The adapter serves to create an abstraction on top of all client adapter implementations (JavaHL, JavaSVN and the SVN command line client). This adapter defines a standard Eclipse extension point that provider implementations can contribute to in order to provide an implementation. The user can then select which provider implementation they wish to use in their client preferences.

The default SVN Client Adapter will be JavaHL, which is the official Java language binding for the Subversion native libraries. JavaHL is developed, maintained and provided as part of the Subversion project and is licensed under the Subversion license.

The core plugin (org.eclipse.team.svn.core) is the Eclipse Team provider implementation for Subversion. It provides access to the SVN instances that are managed by the current workspace. The core plugin allows the team provider to function in a headless environment. This headless environment is already being used by the Buckminster project.

Finally, the UI plugin (org.eclipse.team.svn.ui) uses the core team support to provide a friendly interface to the user. The existing Subclipse UI plugin already implements many of the advanced UI elements that have been added to the CVS UI plugin such as: Quick Diff, Live Annotations, Common History View, Synchronize View including Change Sets and Console view. This is in addition to the more basic use of the Team, Compare and Replace menus. This similarity in the UI makes it easier for existing CVS users to make the transition to SVN, and also smoothes the path by providing the same nice extras that users have become accustomed to. We would like to explore ways to further integrate the UI of these plugins, such as providing a common Repository view and perspective that could be used to house CVS, SVN and any other repositories in one location. There is also the possibility to build common dialogs for operations like Commit. Finally, Subclipse has also gone to great lengths to make the handling of Branches and Tags as familiar as possible to CVS users. See: http://subclipse.tigris.org/branch_tag.html. Subversion and CVS handle branches and tags very differently and the work that has been done by Subclipse in this area has been looked at by the Subversion development community as a possible way to make the handling of tags in Subversion friendlier to CVS users.

Organization

The SVN Team provider project will be organized as follows:

Initial committers

The initial committers will focus on refactoring the existing Subclipse code base to meet the initial objectives of this project, as well as aligning the project with changes in the Platform and Team API. The initial committers are (in alphabetical order):

Subversion committers

Unlike CVS, Subversion is an actively developed open source project. It is important to participate in and coordinate with the Subversion project to help insure that the needs of Eclipse users are taken into consideration as future enhancements are planned and delivered. This proposal includes the following members that have committer access to the Subversion project:

Interested parties

The following Eclipse projects have previously worked with the Subclipse project and have expressed an interest in this proposal.

The following individuals and their organizations have expressed their interest in and support for this proposal.

Developer community

The Subclipse team has a proven track record of operating in an open and transparent manner. Even this proposal has been developed collaboratively by the community using the mailing lists and repository to work as a team. We also have a proven track record of being able to attract and support contributions from the developer community. The Subclipse 1.0 release listed thirty-seven individuals that made code contributions to the project. We expect to continue this tradition and likely expand it greatly as the visibility of the project in the Eclipse community is likely to increase as a result of this process.

The Subclipse team has also made several contributions to Platform Team, Mylar and ALF with the aim of producing a better Team Platform for everyone. Examples include:

User community

As with the Developer community, Subclipse has a proven track record of having a vibrant user community that has always provided valuable assistance to the development process as well as assistance in supporting one another in a respectful and professional manner. The Subversion project itself for that matter has set a high standard of excellence in this area, which other projects have followed.

Subversive Proposal

In March 2006 a second SVN plug-in for Eclipse emerged in the form of a product named Subversive from a company named Polarion. This company has also submitted a proposal to the Eclipse Foundation. See: http://www.eclipse.org/proposals/subversive/.

We believe that our proposal represents the best option for the Eclipse community. The Subclipse project has a 3-year history of operating transparently and is well past the "1.0" stage of the development process. We even have an Eclipse 3.2-specific release available for Callisto users -- a release that leverages several Eclipse 3.2 features. This proposal has the backing of two long time Eclipse Foundation members, SoftLanding Systems and CollabNet, both of whom have a proven track record of supporting open source development in general, and Subversion in particular. We have worked with and have the support of several existing Eclipse projects and just as importantly, we have the backing of the Subversion developer community. Even the primary developer of the JavaSVN library, Alexander Kitaev, has asked to be listed as an interested party and potential contributor to our proposal.

We strongly believe that any Eclipse.org provided support for Subversion should work closely with the Subversion development community. Any proposal that is not based on the official Subversion libraries does not do this.

We invite Polarion to join this proposal and devote their resources to helping us create a single great option that satisfies the needs of the Eclipse and Subversion communities. They have implemented some good ideas in Subversive, and we would encourage them to work with our community to get these features incorporated into our code base, and where necessary, into the Subversion libraries themselves.

Tentative Plan

  • September 2006: Refactored and re-licensed code contribution based on Subclipse
  • December 2006: Initial release as an Eclipse project, supporting Eclipse 3.2.
  • January 2007: Join the release train for Eclipse 3.3
  • July 2007: Possibly move project to Eclipse Platform