I'd like to see the Python source be stored in Subversion instead of CVS, and on python.org instead of sf.net. To facilitate discussion, I have drafted a PEP describing the rationale for doing so, and the technical procedure to be performed.
This is for discussion on python-dev and eventual BDFL pronouncement; if you see a reason not to make such a change, or if you would prefer a different procedure, please speak up. Encouragement and support is welcome, as well :-)
PEP: XXX Title: Migrating the Python CVS to Subversion Version: $Revision $ Last-Modified: $Date$ Author: Martin v. Löwis email@example.com Discussions-To: firstname.lastname@example.org Status: Draft Type: Standards Track Content-Type: text/x-rst Created: 14-Jul-2004 Post-History: 14-Jul-2004
The Python source code is currently managed in a CVS repository on sourceforge.net. This PEP proposes to move it to a subversion repository on svn.python.org.
This change has two aspects: moving from CVS to subversion, and moving from SourceForge to python.org. For each, a rationale will be given.
Moving to Subversion -------------------- CVS has a number of limitations that have been elimintation by Subversion. For the development of Python, the most notable improvements are: - ability to rename files and directories, and to remove directories, while keeping the history of these files. - support for change sets (sets of correlated changes to multiple files) through global revision numbers. - support for offline diffs, which is useful when creating patches.
Moving to python.org -------------------- SourceForge has kindly provided an important infrastructure for the past years. Unfortunately, the attention that SF received has also caused repeated overload situations in the past, to which the SF operators could not always respond in a timely manner. In particular, for CVS, they had to reduce the load on the primary CVS server by introducing a second, read-only CVS server for anonymous access. This server is regularly synchronized, but behind the the read-write CVS repository between synchronizations. As a result, users without commit access can see recent changes to the repository only with a delay.
On python.org, it would be possible to make the repository accessible for anonymous access.
Migration Procedure ===================
To move the Python CVS repository, the following steps need to be executed. The steps are elaborated in more detail in the next sections.
1. Assign passwords for all current committers for use on svn.python.org. User names on SF and svn.python.org should be identical, unless some committer requests a different user name. 2. At the beginning of the migration, announce that the repository on SourceForge closed. 3. 24 hours after the last commit, download the CVS repository. 4. Convert the CVS repository into two subversion repositories, one for distutils and one for Python. 5. Publish the repositories for write access for all committers, and anonymous read access. 6. Disable CVS access on SF.
Assign Passwords ================
Currently, access to Subversion on svn.python.org uses WebDAV over https, using basic authentication. For this to work, authorized users need to provide a password. This mechanism should be used, atleast initially, for the Python CVS as well, since various committers also have a username/password pair for the www SVN repository already.
Alternatives to password-based access include: - Subversion over SSH, using SSH key pairs. This would require to give committers accounts on the machine, which currently is ruled out by the administration policy of svn.python.org. - Subversion over WebDAV, using SSL client certificates. This would work, but would require to administrate a certificate authority.
Downloading the CVS Repository ==============================
The CVS repository can be downloaded from
Since this tarball is generated only once a day, some time after the repository freeze must pass before the tarball can be picked up. It should be verified that the last commit, as recorded on the python-commits mailing list, is indeed included in the tarball.
Converting the CVS Repository =============================
The Python CVS repository contains two modules: distutils and python. Keeping them together will produce quite long repository URLs, so it is more convenient if the Python CVS and the distutils CVS are converted into two separate repositories.
As the repository format, fsfs should be used (requires Subversion 1.1). fsfs has the advantage of being more backup-friendly, as it allows to backup a repository incrementally, without requiring to run any dump commands.
The conversion should be done using cvs2svn utility, available e.g. in the cvs2svn Debian package. The command for converting the Python repository is
cvs2svn -q --encoding=latin1 --force-branch=cnri-16-start --force-branch=descr-branch --force-branch=release152p1-patches --force-tag=r16b1 --fs-type=fsfs -s py.svn.new python/python
The command to convert the distutils repository is
cvs2svn -q --encoding=latin1 --fs-type=fsfs -s dist.svn.new python/distutils
Sample results of this conversion are available at
Publish the Repositories ========================
The repositories should be published at https://svn.python.org/python and https://svn.python.org/distutils. Read-write should be granted through basic authentication to all current SF committers; read-only access should be granted anonymously. As an option, websvn (available e.g. from the Debian websvn package) could be provided.
The current SF project admins should get write access to the password file, in order to create or delete new users.
Disable CVS ===========
It appears that CVS cannot be disabled entirely. Only the user interface can be removed from the project page; the repository itself remains available. If desired, write access to the python and distutils modules can be disabled through a commitinfo entry.