263 lines
8.6 KiB
Plaintext
263 lines
8.6 KiB
Plaintext
PEP: 347
|
||
Title: Migrating the Python CVS to Subversion
|
||
Version: $Revision$
|
||
Last-Modified: $Date$
|
||
Author: Martin v. Löwis <martin@v.loewis.de>
|
||
Discussions-To: <python-dev@python.org>
|
||
Status: Draft
|
||
Type: Informational
|
||
Content-Type: text/x-rst
|
||
Created: 14-Jul-2004
|
||
Post-History: 14-Jul-2004
|
||
|
||
|
||
Abstract
|
||
========
|
||
|
||
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.
|
||
|
||
|
||
Rationale
|
||
=========
|
||
|
||
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 eliminated by
|
||
Subversion. For the development of Python, the most notable
|
||
improvements are:
|
||
|
||
- the 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. Change sets are
|
||
transactional.
|
||
|
||
- atomic, fast tagging: a cvs tag might take many minutes; a
|
||
Subversion tag (svn cp) will complete quickly, and atomically.
|
||
Likewise, branches are very efficient.
|
||
|
||
- 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 lags behind the the read-write
|
||
CVS repository between synchronizations. As a result, users without
|
||
commit access can see recent changes to the repository only after 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 upon in the following sections.
|
||
|
||
1. Collect SSH keys for all current committers, along with usernames
|
||
to appear in commit messages.
|
||
|
||
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 a Subversion repository.
|
||
|
||
5. Publish the repository with write access for committers, and
|
||
read-only anonymous access.
|
||
|
||
6. Disable CVS access on SF.
|
||
|
||
|
||
Collect SSH keys
|
||
----------------
|
||
|
||
After some discussion, svn+ssh was selected as the best method
|
||
for write access to the repository. Developers can continue to
|
||
use their SSH keys, but they must be installed on python.org.
|
||
|
||
In order to avoid having to create a new Unix user for each
|
||
developer, a single account should be used, with command=
|
||
attributes in the authorized_keys files.
|
||
|
||
The lines in the authorized_keys file should read like this
|
||
(wrapped for better readability)::
|
||
|
||
command="/usr/bin/svnserve --root=/svnroot -t
|
||
--tunnel-user='<username>'",no-port-forwarding,
|
||
no-X11-forwarding,no-agent-forwarding,no-pty
|
||
ssh-dss <key> <comment>
|
||
|
||
As the usernames, the real names should be used instead of
|
||
the SF account names, so that people can be better identified
|
||
in log messages.
|
||
|
||
|
||
Downloading the CVS Repository
|
||
------------------------------
|
||
|
||
The CVS repository can be downloaded from
|
||
|
||
http://cvs.sourceforge.net/cvstarballs/python-cvsroot.tar.bz2
|
||
|
||
Since this tarball is generated only once a day, some time must pass
|
||
after the repository freeze 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.
|
||
|
||
After the conversion, the converted CVS tarball should be kept
|
||
forever on www.python.org/archive/python-cvsroot-<date>.tar.bz2
|
||
|
||
|
||
Converting the CVS Repository
|
||
-----------------------------
|
||
|
||
The Python CVS repository contains two modules: distutils and python.
|
||
The python module is further structured into dist and nondist,
|
||
where dist only contains src (the python code proper). nondist
|
||
contains various subdirectories.
|
||
|
||
These should be reorganized in the Subversion repository to get
|
||
shorter URLs, following the <project>/{trunk,tags,branches}
|
||
structure. A project will be created for each nondist directory,
|
||
plus for src (called python), plus distutils. Reorganizing the
|
||
repository is best done in the CVS tree, as shown below.
|
||
|
||
The fsfs backend should be used as the repository format (which
|
||
requires Subversion 1.1). The fsfs has the advantage of being more
|
||
backup-friendly, as it allows incremental repository backups, without
|
||
requiring any dump commands to be run.
|
||
|
||
The conversion should be done using the cvs2svn utility, available
|
||
e.g. in the cvs2svn Debian package. As cvs2svn does not currently
|
||
support the project/trunk structure, each project needs to be
|
||
converted separately. To get each conversion result into a separate
|
||
directory in the target repository, svnadmin load must be used.
|
||
In summary, the conversion script is::
|
||
|
||
#!/bin/sh
|
||
rm cvs2svn-*
|
||
rm -rf python py.new
|
||
tar xjf python-cvsroot.tar.bz2
|
||
rm -rf python/CVSROOT
|
||
svnadmin create --fs-type fsfs py.new
|
||
mv python/python python/orig
|
||
mv python/orig/dist/src python/python
|
||
mv python/orig/nondist/* python
|
||
# nondist/nondist is empty
|
||
rmdir python/nondist
|
||
rm -rf python/orig
|
||
for a in python/*
|
||
do
|
||
b=`basename $a`
|
||
cvs2svn -q --dump-only --encoding=latin1 --force-branch=cnri-16-start \
|
||
--force-branch=descr-branch --force-branch=release152p1-patches \
|
||
--force-tag=r16b1 $a
|
||
svn mkdir -m"Conversion to SVN" file:///`pwd`/py.new/$b
|
||
svnadmin load -q --parent-dir $b py.new < cvs2svn-dump
|
||
rm cvs2svn-dump
|
||
done
|
||
|
||
Sample results of this conversion are available at
|
||
|
||
http://www.dcl.hpi.uni-potsdam.de/pysvn/
|
||
|
||
|
||
Publish the Repository
|
||
------------------------
|
||
|
||
The repository should be published at https://svn.python.org/projects.
|
||
Read-write access should be granted through basic authentication to
|
||
all current SF committers; read-only anonymous access should also be
|
||
granted. Read-write access will go through
|
||
svn+ssh://pythondev@svn.python.org/projects.
|
||
|
||
As an option, websvn (available e.g. from the Debian websvn package)
|
||
could be provided. Unfortunately, in the test installation, websvn
|
||
breaks because it runs out of memory.
|
||
|
||
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 CVS commitinfo entry.
|
||
|
||
|
||
Discussion
|
||
----------
|
||
|
||
Several alternatives had been suggested to the procedure above.
|
||
The rejected alternatives are shortly discussed here:
|
||
|
||
- create multiple repositories, one for python and one for
|
||
distutils. This would have allowed even shorter URLs, but
|
||
was rejected because a single repository supports moving code
|
||
across projects.
|
||
|
||
- Nick Bastin has offered to host a Perforce repository, instead
|
||
of using Subversion. Details of that offer are not clear yet.
|
||
|
||
- Several people suggested to create the project/trunk structure
|
||
through standard cvs2svn, followed by renames. This would have
|
||
the disadvantage that old revisions use different path names
|
||
than recent revisions; the suggested approach through dump files
|
||
works without renames.
|
||
|
||
- Several people also expressed concern about the administrative
|
||
overhead that hosting the repository on python.org would cause
|
||
to pydotorg admins. As a specific alternative, BerliOS has been
|
||
suggested. The pydotorg admins themselves haven\'t objected
|
||
to the additional workload; migrating the repository again if
|
||
they get overworked is an option.
|
||
|
||
- Different authentication strategies were discussed. As
|
||
alternatives to svn+ssh were suggested
|
||
|
||
* Subversion over WebDAV, using SSL and basic authentication,
|
||
with pydotorg-generated passwords mailed to the user. People
|
||
did not like that approach, since they would need to store
|
||
the password on disk (because they can't remember it); this
|
||
is a security risk.
|
||
|
||
* Subversion over WebDAV, using SSL client certificates. This would
|
||
work, but would require us to administer a certificate authority.
|
||
|
||
|
||
Copyright
|
||
=========
|
||
|
||
This document has been placed in the public domain.
|
||
|
||
|
||
..
|
||
Local Variables:
|
||
mode: indented-text
|
||
indent-tabs-mode: nil
|
||
sentence-end-double-space: t
|
||
fill-column: 70
|
||
End:
|