Cherry picking merge sensitive logs

The 'svn log -g' feature, as currently spec'd, only displays merged
revisions as children of a merging revision. For example, if r14 merged
r13 and r12 from 'branches/a' to 'trunk', we only return log information
for r13 and r12 if for 'svn log -g trunk' with some range that includes r14.

This make sense, but in some ways, it would seem useful to be able to
run 'svn log -g -r13 trunk', and have the information from r13 get
returned. After all, r13 is now part of trunk, by virtue of the merge
in r14.

So, these are my questions:
1) Is this desired behavior?

2) What is the difficulty in determining whether or not a particular
revision is part of a given path, either as a direct commit, or as the
result of a merge? (<thinking-to-self>Wait a second, that's what
svn:mergeinfo is for. Is that all I need? It just seems too
easy...</thinking-to-self>)

3) How would this be displayed? Would it be possible to easily
determine the merging revision so that the output would be consistent
with other output from 'svn log -g'?

-Hyrum