Below is the file 'tests/t_log_to_file.at' from this revision. You can also download the file.
# -*- Autoconf -*-
AT_SETUP([check --log])
MONOTONE_SETUP
AT_DATA(input.txt, [random content
])
AT_CHECK(MONOTONE add input.txt, [], [ignore], [ignore])
AT_CHECK(MONOTONE --branch=testbranch --log=log.log commit -m "test", [], [stdout], [ignore])
AT_CHECK(QGREP('^monotone:' stdout), [1])
AT_CHECK(QGREP('^monotone:' log.log), [0])
AT_CLEANUP