t/lib-t6000: style fixes

Mostly fixes to initial indentation with 8-SP (they should be HT)
and wrapping long lines.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
topology tests: teach a helper to take abbreviated timestamps

The on_committer_date helper in t/lib-t6000 is used in t6002 and
t6003 with timestamps on a single day within a single minute
(i.e. 1971-08-16 00:00) and the tests repeat this over and over.

The actual value of the timestamp, however, does not matter very
much; only their relative ordering does.

Introduce another helper to expand only the suffix of the timestamp
to a full timestamp to make the lines shorter, and use it in this
helper.  Also, because all the commits in the test are made with
specific GIT_COMMITTER_DATE, stop unsetting it at the end of the
helper.

We'll be specifying the author timestamp to these test commits in a
later patch, which will be helped with this change.

Also remove a test that was commented-out from t6003; it used to
test a commit with the same parent listed twice, which was allowed
by mistake but was fixed long time ago.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
t6003: add --date-order test

The "--date-order" output is a slight twist of "--topo-order" in
that commits from parallel histories are shown in their committer
date order without an attempt to clump commits from a single line
of history together like --topo-order does.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
topology tests: teach a helper to set author dates as well

Introduce on_dates helper that is similar to on_committer_date but
also sets the author date, not just the committer date.

At this step, just set the same timestamp to the author date as the
committer date, as no test looks at author date yet.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
t6003: add --author-date-order test

Tweak the --topo/date-order test vector a bit and mark the author
dates of two commits (a2 and a3) earlier than their own committer
dates, making them much older than other commits that are made on
parallel branches to simulate the case where a long running topic
was rebased recently.

They will show up as recent in the --date-order output due to their
timestamps, but they appear a lot later in the --author-date-order
output, even though their committer timestamp says otherwise.

Signed-off-by: Junio C Hamano <gitster@pobox.com>