[PATCH v2 0/6] reflog docs and date-formatting

This is a repost of the patches in:

  http://thread.gmane.org/gmane.comp.version-control.git/299201/focus=299236

since I don't think they got picked up at all.

The contents are the same, but with one extra patch (the 4th) that was
posted mid-discussion.

The only other review comment is that patch 5 might want to editorialize
the weirdness of "raw-local" more. I think I'm comfortable leaving it
as-is based on my response in:

  http://article.gmane.org/gmane.comp.version-control.git/299312

but I could be persuaded otherwise.

The final patch, "--date=unix" doesn't _really_ solve Ted's problem,
because there's still no way to give multiple date formats in the same
line, nor use "%gd" as both the reflog index and as the date. So I'm
assuming he'll still build "%gt" or similar on top of this, and only in
the long run will we get to "%(reflog-date:unix)" or whatever.

So I think it's still valuable as a minor feature for other formatting
needs, and as a potential building block for later. The earlier patches
are all immediately useful as clarifications.

  [1/6]: doc/rev-list-options: clarify "commit@{Nth}" for "-g" option
  [2/6]: doc/rev-list-options: explain "-g" output formats
  [3/6]: doc/pretty-formats: describe index/time formats for %gd
  [4/6]: doc/pretty-formats: explain shortening of %gd
  [5/6]: date: document and test "raw-local" mode
  [6/6]: date: add "unix" format

-Peff