simplify HistoryIterator message ordering

rename reverse -> oldest_first, which is more obvious what it does.
Then, honor it entirely - if you specify no `after` endpoint, we default
to the beginning of message history, similar to how `before` defaults to
the end of message history.

This is a breaking change, and will change the behavior of any iterator
that previously would have been returning messages in a weird order for
limits over 100

`for msg in history(reversed=True, limit=300)` would return the newest
300 messages, in a messed up order (100..0, 200..100, 300..200).
`for msg in history(oldest_first=True, limit=300)` will now return the
oldest 300 messages in order. And so on.

`for msg in history(after=msg)` is unchanged, this previously would
return the oldest 100 messages after `msg`, oldest->newest order, and
still will.

1 files changed, 2 insertions, 2 deletions

diff --git a/docs/locale/ja/LC_MESSAGES/api.po b/docs/locale/ja/LC_MESSAGES/api.po
index c947dbda..f381f28d 100644
--- a/docs/locale/ja/LC_MESSAGES/api.po
+++ b/docs/locale/ja/LC_MESSAGES/api.po
@@ -7361,8 +7361,8 @@ msgid "Same as ``around`` in :meth:`history`."
 msgstr ":meth:`history` での ``around`` と同じです。"
 
 #: discord.TextChannel.purge:25 of
-msgid "Same as ``reverse`` in :meth:`history`."
-msgstr ":meth:`history` での ``reverse`` と同じです。"
+msgid "Same as ``oldest_first`` in :meth:`history`."
+msgstr ":meth:`history` での ``oldest_first`` と同じです。"
 
 #: discord.TextChannel.purge:26 of
 msgid "If True, use bulk delete. bulk=False is useful for mass-deleting a bot's own messages without manage_messages. When True, will fall back to single delete if current account is a user bot, or if messages are older than two weeks."