As a verb, 'setup' is spelled 'set up'. “diff commands such as
diff-files” scans better without a comma. Clarify that shallow
and deep are special non-boolean values for format.thread rather
than boolean values with some other name.
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>