Version Control With Subversion Source

repository-relative URLs).

Some examples specifically grep for "URL". Most of those now grep for
"^URL" so as not to distract from the larger point of those examples
with the additional "Relative URL" output line.

* en/book/ch03-advanced-topics.xml
* en/book/ch04-branching-and-merging.xml
* en/book/ref-svn.xml
Update uses of 'svn info' to consider the "Relative URL" output line.