dan forys

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Step by step: Moving code between Subversion repositories

Posted on 2008-07-23 - Comments

As many coders will tell you, there reaches a point where you realise that you absolutely, positively must keep your code in a a revision control system. In my working life, I’ve used Microsoft’s ageing SourceSafe and more recently the vastly superior SubVersion (SVN).

There’s many powerful GUIs out there which you can use to interact with SVN, and make the checking out and checking in very easy. If you primarily use a desktop GUI (like me), then chances are you use a SVN client GUI to interact with SVN on a day-to-day basis.

But what happens when you need to move code between repositories?

I first realised I needed to reorganise my repositories when my single "clients" repository was growing unwieldy. It was one large repository, with all my client work organised into folders by the project name. This method keeps things very tidy, but increments the version numbers with every commit on every project and means you have a very long root log.

A better way, I realised, is to keep the unrelated projects organised in their own repositories – but how to move the code out of my client repository into a new one?

To do this, you’ll need shell access to your SVN server (surely you do – otherwise, how do you create your repositories?)

SVN provides the svnadmin dump command to export data from your repository. In my case, to dump the contents of my entire clients repository, I did the following:

svnadmin dump clients > clients-dumpfile

which creates a text file called clients-dumpfile containing all the revision data for my clients repository. Note that this can create a very large file, as it’s not stored in the ultra-efficient space-saving SVN database any longer.

Say I want to move all my code from a folder called client-1, and put it in its own repository. First thing I need to do, is to create the destination repository:

svnadmin create client-1-repository

Now – the dumpfile contains all the code for all the projects, so how do I filter out the other projects? (this is all one line)

cat clients-dumpfile | svndumpfilter include client-1 --drop-empty-revs --renumber-revs > client-1-filtered-dumpfile

What does this do? It takes the previously created clients-dumpfile and sends it through the svndumpfilter program. I’ve told it to include the client-1 folder (and throw away everything else). I’ve told it to drop the empty revisions left behind by the thrown away data, and renumber the rest of the revisions so my new repository is nicely sequentially numbered. The results from svndumpfilter are output into a new file called client-1-filtered-dumpfile.

Finally, you simply load the data into the new repository:

svnadmin load client-1-repository < client-1-filtered-dumpfile

Hopefully, you now have a populated repository with your clients' code.