Call ref_transaction_commit with QUIET_ON_ERR and use the strbuf that is
returned to print a log message if/after the transaction fails.
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Ronnie Sahlberg <sahlberg@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> Acked-by: Michael Haggerty <mhagger@alum.mit.edu>