> So if you can patch ‘testsuite’ directly, that’s better.

I guess that the following line raises the error:

( $at_check_trace; env PATH="$PWD" "$wdiff_bin" foo.txt bar.txt

'wdiff_bin' is defined like this:

wdiff_bin="`which wdiff`"

Why does it fail to find the binary?  Is it connected with 'env'?