svn trying to merge changes from trunk to branch

We had a branch Branch1 that we then branched off again, Branch1A. All the while we've been merging trunk changes into Branch1 and then merging change from Branch1 into Branch1A

开发者_运维百科Branch1 was then re-integrated with trunk. And now we want to merge those changes and any other trunk changes into Branch1A.

However when I try to do this merge, I get hundreds of tree conflicts?

What have I done wrong?

I think the Tree conflicts are caused by "repeating merge"(SVN think it's right)

1. When you merge code from trunk to Branch1, the Branch1 records the mergeinfo about trunk;
2. When you merge code from Branch1 to Branch1A, the Branch1A records the mergeinfo about Branch1.
3. When you merge code from trunk to Branch1A, image that these is one file added in trunk, then merged to Branch1 by step1, then merged to Branch1A by step2. but in the Branch1A, there is no svn:mergeinfo recorded about trunk, so it will merge that file again from trunk to Branch1A, then a tree conflict happened(local added, incoming added, upon merge).