$ cat .hg/hgrc [hooks] pretxncommit.whitespace = .hg/check_whitespace.py $ echo 'a ' >> a $ hg commit -A -m 'add new line with trailing whitespace' a, line 2: trailing whitespace added commit message saved to .hg/commit.save transaction abort! rollback completed abort: pretxncommit.whitespace hook exited with status 1 $ sed -i 's, *$,,' a $ hg commit -A -m 'trimmed trailing whitespace' a, line 2: trailing whitespace added commit message saved to .hg/commit.save transaction abort! rollback completed abort: pretxncommit.whitespace hook exited with status 1