fix reflog approxidate parsing bug

In get_sha1_basic, we parse a string like HEAD@{10 seconds ago}:path/to/file into its constituent ref, reflog date, and path components. We never actually munge the string itself, but instead keep offsets into the string with their associated lengths. When we call approxidate on the contents inside braces, however, we pass just a string without a length. This means that approxidate could sometimes look past the closing brace and (erroneously) interpret the rest of the string as part of the date. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>