Fix non-empty $CDPATH causing failed tests.
If CDPATH contains '.', every cd command prints the target path,
which causes additional output in tests and makes them fail.
% add file
adding qqq.txt
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test 1:16b24da7e457
test2 1:16b24da7e457
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* test 1:9f1b7e78eff8
* test2 1:9f1b7e78eff8