Every time I have to deal with svn:externals in SVN, I forget the command line syntax. Every single damn time. Normally, I use SVN GUI clients, such as SmartSVN, which make it very simple to add an svn:externals property. But for command line, it always takes looking at 25 different sites on google, which are all incredibly unhelpful for this question for some reason. Trying "svn help propset" on the command line was bloated and equally useless.

So this time I needed to write it down and make sure everyone who needed help with svn:externals would find exactly what they need here. I hope this page will soon come up on top of all the unhelpful results on google for "propset svn:externals" and other related queries.

The Problem

I want to set a simple svn:externals property in one of my project's directories, lets say 'plugins' (talking about WordPress here). The outcome would be a directory called 'akismet' within 'plugins' that points to a remote svn url.

Various combinations of trying to do it produced pathetic results, like

svn propset svn:externals akismet http://plugins.svn.wordpress.org/akismet/trunk
svn: Setting property on non-local target 'http://plugins.svn.wordpress.org/akismet/trunk' needs a base revision

svn propset svn:externals . akismet http://plugins.svn.wordpress.org/akismet/trunk
svn: Error parsing svn:externals property on 'akismet': '.'

svn propset svn:externals akismet http://plugins.svn.wordpress.org/akismet/trunk akismet
svn: Setting property on non-local target 'http://plugins.svn.wordpress.org/akismet/trunk' needs a base revision

The Solution

Finally, thanks to this post, I found the right command:

svn propset svn:externals 'akismet http://plugins.svn.wordpress.org/akismet/trunk' .
property 'svn:externals' set on '.'

Note that dot at the end of the command and the quotes around the directory name and url.

Now commit via

svn commit

and then

svn up
Fetching external item into 'akismet'
A    akismet/akismet.gif
A    akismet/akismet.php
A    akismet/readme.txt
Updated external to revision 127962.
 
Updated to revision 16.

There, was it that hard, forum gurus and blog fiends?

Edit: in order to set multiple directory/url pairs in a single svn:externals property, you should put the individual dir/url pairs into a file (let's call it 'svn.externals'), like so

akismet http://svn.wp-plugins.org/akismet/trunk
all-in-one-seo-pack http://svn.wp-plugins.org/all-in-one-seo-pack/trunk

and then apply the property using

svn propset svn:externals -F svn.externals .

You should also just check in 'svn.externals' to easily keep track of it.