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Dirac SVN Repository


SVN Repository Organization


In a subversion repository, the organization of the paths is of fundamental importance for the everyday work and usability. We want to follow the standard (but not enforced) basic hierarchy of a project hosted on SVN, which consists of the 3 directories:
  • trunk: the main trunk of development
  • tags: fixed versions of the project identified by symbolic names
  • branches: branches of evolution of the project parallel to the trunk

Out development model requires the necessity to have package level tags and branches. At the same time, we need something that can be used as a tag on the whole project. Moreover, LHCb unique CVS repository is hosting many CMT projects and a global tag is pointless, but we can profit from the possibility of check out a complete tagged project in one command.


The repository contains the 3 main directories packages, projects and distribution.

packages will contain one directory per package, each of them with the 3 standard directories trunk, tags and branches. In case of CMT "hats", we can have packages/Hat/Package/trunk etc. The list of known packages can be obtained scanning the content of the directory packages, going down one level to take into account the possibility of hats. The scanning is very inefficient, so we can add a property called modules to the packages directory containing a newline-separated list of the known modules. This property can be updated automatically with a cron job or on demand.


The projects directory will contain one directory per hosted project (as container of packages), with the usual 3 standard directories. The content of the trunk for one this projects is only the content of the cmt directory that lives at the project level:

  • projects/DIRAC/trunk/project.cmt

The distribution directory contains the 3 standard directories. The tags and branches directory will have one subdirectory per hosted project, each of them containing one directory per "global tag". Those global tag directories will be empty and the internal structure will be described with svn externals definitions. External definitions are metadata of a directory that instruct svn to populate the directory checking out the subdirectories from other svn locations (more or less as cvs module aliases). The trunk directory will contain one empty directory per project, that, with the externals definitions, will allow to check out the trunks of all the related packages in one go.
Note: due to the non-locality of the external definitions (svn allows to check out from different repositories), we cannot use the same distribution sub directory for the public anonymous access and the read/write access, so distribution/trunk/DIRAC should be used by developers, while anonymous users will have to use distribution/tags/DIRAC/DIRAC_HEAD which will checkout the same files as trunk, but using the read-only http protocol.


svn Quick Reference for cvs Users

Environment variables for the repositories:
    anonymous read-only access
    read-write access


  • Checkout head version of a package
    • cvs
      cvs -d $DIRACCVS checkout DiracConfig
    • svn
      svn checkout $DIRACSVN/packages/DiracConfig/trunk DiracConfig
  • Checkout tagged version of a package
    • cvs
      cvs -d $DIRACCVS checkout -r v20r0 DiracConfig
    • svn
      svn checkout $DIRACSVN/packages/DiracConfig/tags/v20r0 DiracConfig
  • Checkout a complete project head version
    • cvs (Dirac only)
      mkdir DIRAC
      cd DIRAC
      cvs -d $DIRACCVS checkout all
    • svn
      svn checkout $DIRACSVN/distribution/trunk/DIRAC
    • svn read-only access
      svn checkout $DIRACSVN/distribution/tags/DIRAC/DIRAC_HEAD DIRAC
  • Checkout tagged version of a complete project
    • cvs (Dirac only)
      mkdir -p DIRAC/DIRAC_v20r0
      cd DIRAC/DIRAC_v20r0
      cvs -d $DIRACCVS checkout -r DIRAC_v20r0 all
    • svn
      mkdir DIRAC
      cd DIRAC
      svn checkout $DIRACSVN/distribution/tags/DIRAC/DIRAC_v20r0


The commit is identical in CVS and Subversion
  • Commit the changes in the current directory (and subdirectories)
    • cvs
      cvs commit 
    • svn
      svn commit
  • Commit the changes of a single file
    • cvs
      cvs commit "myfile"
    • svn
      svn commit "myfile"


I want to distinguish between two use cases:
  • simple update: synchronize the local copy with the latest (or a specific) revision of the repository
  • update with tags: move from a tagged local version to the head one or to a branch

Simple Update

Nothing really special:
  • cvs
    cvs update
  • svn
    svn update
The way to select a revision or a moment in time a slightly different, but easy to sort out using the help.

Update with Tags

This is the complex part, since tags do not exists (as such) in Subversion. With SVN, tags are represented by copies of the trunk directory, so moving the working copy from a tag to another (or trunk or branch) means changing the path of the origin of the working copy.
  • Move the working copy from the current tag to the trunk/HEAD (assuming you are in the top directory of the package)
    • cvs
      cvs update -APd
    • svn
      svn switch $DIRACSVN/packages/MyPackage/trunk
  • Move the working copy from the current tag to the another tag (assuming you are in the top directory of the package)
    • cvs
      cvs update -Pd -r other_tag
    • svn
      svn switch $DIRACSVN/packages/MyPackage/tags/other_tag

Check for updates in the repository

To just check if there are changes in the repository that you didn't get yet, you can do a "dry-run" update with cvs. That does not exist in svn, you have to ask the status of the repository.
  • cvs
    cvs update -n
  • svn
    svn status -u
    svn status --show-updates

Comparison (diff)

  • Comparison between the base of the working copy and the working copy
    • cvs
      cvs diff -u
    • svn
      svn diff
  • Comparison between two tags (or branch, or trunk)
    • cvs
      cvs diff -u -r tag1 -r tag2
    • svn
      svn diff $DIRACSVN/packages/MyPackage/tags/tag1 $DIRACSVN/packages/MyPackage/tags/tag2

Tagging and Branching

  • Tag the working copy (assuming you are in the top directory of the package)
    • cvs
      cvs tag the_tag
    • svn
      svn cp .  $DIRACSVN/packages/MyPackage/tags/the_tag
  • Tag the head version in the repository
    • cvs
      cvs rtag the_tag MyPackage
    • svn
      svn cp $DIRACSVN/packages/MyPackage/trunk $DIRACSVN/packages/MyPackage/tags/the_tag
Branching is done in CVS addind the option '-b' to the command 'tag', while in Subversion it is enough to replace tags with branches.


Help desk reported problems

These are just to remember them.

-- Main.JoelClosier - 08 Jun 2009

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Topic revision: r1 - 2009-06-08 - JoelClosier
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