[Boost-build] Unconditional shell command without <conditional>?

Subject: [Boost-build] Unconditional shell command without <conditional>?
From: Boris Schaeling (boris_at_[hidden])
Date: 2011-01-29 09:26:00

I'm converting a Makefile to a Jamfile and need to define a macro with a  
Subversion revision number. I came up with this Jamfile:

project : requirements <conditional>@add-svn-revision ;
rule add-svn-revision ( properties * )
{
   local svn_ref = [ SHELL "svnversion -n" ] ;
   return <define>SVN_REV=\"$(svn_ref)\" ;
}

While this works I wonder if there is a better (shorter) way? Can I inline  
the call to "svnversion -n" without using <conditional>?

Boris