Blocking Merge-Unaware Clients

[Jack Bates]

Thank you for the svnbook - it continues to be outstanding
documentation.

The section on "Blocking Merge-Unaware Clients" was useful last night,
and I created a "start-commit" hook to check for "mergeinfo" in
capabilities. However, it would have been faster if there were a
concrete example of the correct way to check, right in the book.

Would it be possible to add a code snippet for checking capabilities for
"mergeinfo" to the "Blocking Merge-Unaware Clients" section?