[MERGE][Bug #162469] log displayers for custom revision

[Robert Collins]

Robert Collins has voted resubmit.
Status is now: Resubmit
Comment:
A few issues.

some of your docstrings do not have a proper sentence as the first line 
(see PEP-8/HACKING)

This hunk:
@@ -664,6 +681,9 @@
              to_file.write('\n')
              for parent_id in revision.rev.parent_ids:
                  to_file.write(indent + 'parent: %s\n' % (parent_id,))
+
+        # show custom properties
+        self.show_properties(revision.rev.properties)

          author = revision.rev.properties.get('author', None)

The comment is not needed, nor is the extra vertical whitespace. (Too 
many comments can detract from readability by making the code area not 
fit on screen compactly.).

Lastly you should test error cases - what happens if there is a bad 
plugin function, will bzr blow up/degrade gracefully/undefined? Does log 
work correctly with no plugins present (you have to explicitly test this 
because selftest loads plugins).

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C9c28f0520803090718l3df6e2a8hadf3b740d8e70270%40mail.gmail.com%3E