Recursively compare two directories with diff -r without output on broken links

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http://unix.stackexchange.com – I am using diff -r a b to recursively compare directories a and b. It often happens though that there are some broken links (the same broken links in both a and b directories and to the same, non-existing targets). diff then outputs error messages for those cases and exists with a non-zero exit code though I would like it to stay silent and exit with 0 as the directories are the same in my book. How can I do that? (HowTos)