Quit passing 'now' to date code

Commit b841d4ff43 (Add `human` format to test-tool, 2019-01-28) added
a get_time() function which allows $GIT_TEST_DATE_NOW in the
environment to override the current time. So we no longer need to
interpret that variable in cmd__date().

Therefore, we can stop passing the "now" parameter down through the
date functions, since nobody uses them. Note that we do need to make
sure all of the previous callers that took a "now" parameter are
correctly using get_time().

Signed-off-by: Stephen P. Smith <ischis2@cox.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/cache.h b/cache.h
index b1da1ab..48d4287 100644
--- a/cache.h
+++ b/cache.h
@@ -1516,8 +1516,7 @@ struct date_mode {
 struct date_mode *date_mode_from_type(enum date_mode_type type);
 
 const char *show_date(timestamp_t time, int timezone, const struct date_mode *mode);
-void show_date_relative(timestamp_t time, const struct timeval *now,
-			struct strbuf *timebuf);
+void show_date_relative(timestamp_t time, struct strbuf *timebuf);
 void show_date_human(timestamp_t time, int tz, const struct timeval *now,
 			struct strbuf *timebuf);
 int parse_date(const char *date, struct strbuf *out);
@@ -1526,7 +1525,7 @@ int parse_expiry_date(const char *date, timestamp_t *timestamp);
 void datestamp(struct strbuf *out);
 #define approxidate(s) approxidate_careful((s), NULL)
 timestamp_t approxidate_careful(const char *, int *);
-timestamp_t approxidate_relative(const char *date, const struct timeval *now);
+timestamp_t approxidate_relative(const char *date);
 void parse_date_format(const char *format, struct date_mode *mode);
 int date_overflows(timestamp_t date);