Fix notification for merges from pre-1.5 repos using 1.5 client, cherry-picking multiple changesets.
Fix notification for merges from pre-1.5 repos using 1.5 client,
cherry-picking multiple changesets.

Before this change, we got the merge notification for only the first
changeset as it appears in the command line, though merge did happen
for all the changesets:

$ svn co http://svn.collab.net/repos/svn/branches/1.5.x svn_1.5.x
$ cd svn_1.5.x
$ svn merge -c29185 -c29186 -c29188 http://svn.collab.net/repos/svn/trunk .
--- Merging r29185 into '.':
    path1
    path2
    ...


* subversion/libsvn_client/merge.c
  (do_directory_merge): Reset notify_b->cur_ancestor_index to -1,
   before each merge drive.

Found by: arfrever


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@869451 13f79535-47bb-0310-9956-ffa450edef68

wbond/subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion