On Subversion

I’ve recently started using the Subversion Source Control system a lot more. It really has got pretty stable now and I feel happy about telling people that they should consider migrating to Subversion from CVS (or in fact pretty much any other Source Control tool) as soon as they can. Atomic checkins, offline features, scalibility, useful and easy tags and branching, and lots of other good stuff all make it a compelling tool.

One thing that has helped Subversion recently is the improved documentation available. An example of this is Mike Mason‘s new book Pragmatic Version Control Using Subversion. I have to say right now that I’m an old friend and colleague of Mike’s and also reviewed the book, so I am completely biased, but I think its a brilliant tutorial to getting started with Subversion, and a handy reference to have around.

Mike’s also recently helped me out with a couple of things that weren’t in the book, so I wanted to share them here.

Firstly, if you’ve been following my blog recently you’ll know I’ve been using Cygwin a lot more. One of the things that Mike does very well is show how powerful and easy the svn command line client is. I was using the standard Windows download of Subversion with Cygwin, but apparently this is a really bad idea. Apart from not using the right kind of paths, you can apparently also get file corruption.

Anyway, this is easy to change – open up the Cygwin installer and choose to use its version of Subversion – its in the devel folder. Cygwin will automatically update your path so that your Cygwin version of svn is used rather than the previous one you installed. You’ll also need to repeat any changes you made to your Subversion config file – the Cygwin version will appear in the ~/.subversion/ directory. If you’ve already setup Putty, Plink and Pageant to manage your SSH identity this will still work – my config file has one change to support this:

[tunnels]

ssh = $SVN_SSH /c/tools/putty/PLINK.EXE

The second thing is to do with deletes. During the course of a development episode, I might well delete some old files. When I perform a svn status I will get a bunch of files showing as ! meaning that they have been removed by something other than a Subversion request. In fact I’ll get output a bit like this:

$ svn st

A      src/Core/Generators/NewGenerator.cs

!      src/Core/Generators/StandardDotNetUpperCaseGuidGenerator.cs

!      src/Core/Generators/IGuidGenerator.cs

Typically I then manually run a svn rm command for each of these, but this can get a little tedious after you’ve done it once. So since I’m using Cygwin, I can use some script to get the shell to do it automatically for me:

$ svn st | awk '$1 == "!"' | cut -c 2- | xargs svn rm

D         src/Core/Generators/StandardDotNetUpperCaseGuidGenerator.cs

D         src/Core/Generators/IGuidGenerator.cs

Now I don’t want to have to remember to do this every time, so I add this to the .profile file in my Cygwin home directory:

alias svnrmdeleted='svn st | awk "$1 == \"!\"" | cut -c 2- | xargs svn rm'

Now to remove from Subversion all deleted files I just type svnrmdeleted .

UpdateMatt Ryall came back with the update to the above using awk rather than grep. (Otherwise you might end up deleting files with actual “!”‘s in the name). He also grappled the required escaping to get the alias to work. (Thanks Matt!)

Update – Dan Bodart has since told me how to do this in plain Windows shell (Thanks Dan!):

  • for /f "usebackq tokens=2" %i in (`"svn st | findstr !"`) do svn rm %i

So, in summary – go use Subversion! Even if you are mostly a Windows user then try using its command line and ask some friendly UNIX- (or Windows Script-) savvy people how to automate some things you do often.

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