Revision 1669743

Follow-up to r1654934:
Relax the size check in the FSFS representation sharing code to make it as
effective as in earlier releases.

The size check has been to strict and would not allow two matching reps to
have a different base representation, e.g. mod on /trunk and add-without-
history on a branch.  Mainly depending on the merge policy (catch-up vs.
cherry-pick), this resulted in detecting and eliding fewer instances of
redundant representations.  Hence, larger repositories.

* subversion/libsvn_fs_fs/transaction.c
  (get_shared_rep): Care about the on-disk size only if the fulltext /
                    expanded size is not known - which would be the case
                    for e.g. PLAIN representations.