How can I diff two files while ignoring diffs I've already marked as known

I'm trying to maintain two parallel versions开发者_StackOverflow of the same stuff. Occasionally, I spend some time synching them to each other.

One way I've found to do this is to diff between each pair of files and look at the differences.

The problem is that there are a bunch of differences that I know about. They will continue to be different. I'm looking for the other stuff.

Is there a diff tool out there that will allow me to mark particular diffs are known/ignore?

I'm in the linux env using SVN. I'm fine with using windows based utilities.

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In Beyond Compare you can select a block of differences and mark it as ignored. It will switch the coloring and filtering so it's displayed as a match instead, though it doesn't persist across comparisons. It supports both Linux and Windows.