SVN-4845: Avoid partial commits that break mergeinfo

Hi,

prompted by IRC discussion, I also created

        https://issues.apache.org/jira/browse/SVN-4845

for my initial issue: Users unknowingly breaking the association of
mergeinfo with the associated dirs/files by selective commits.

Like for SVN-4844, it would be nice if one also could figure out smarts
to transparently repair the state of repositories that suffer from
this, but I guess this is a lot harder.

So I'd like to prompt addition of a switch like

        svn commit --allow-broken-mergeinfo

to force the current behaviour and change the default to include a
check if

a) There is an object in the commit which has mergeinfo stored in a
   directory that itself is not part of the commit or
b) there is mergeinfo in the commit and some object affected by that is
   not included.

The commit should be aborted if this is the case. Thoughts?

Alrighty then,

Thomas

-- 
Dr. Thomas Orgis
HPC @ Universität Hamburg