Any merge-tracking merge, be it an automatic merge or a cherry pick can, based
on the preexisting mergeinfo on the WC target, split a merge into multiple
editor drives. Normally this isn't a problem, but if an earlier editor drive
aborts due to a conflict, mergeinfo should be recorded that only describes the
partial completion of the merge. Unfortunately this is not the case and the
mergeinfo for the entire requested merge is recorded. This means that once the
conflict is resolved, a repeat of the original merge does not not attempt to
apply the still un-merged changes.
A detailed example is described here:
http://svn.haxx.se/dev/archive-2013-01/0482.shtml