Update cros_changelog to support sort-by-date option.

Update cros_changelog to support sort-by-date option.

Other changes:
  1. Clean up revision handling to be more forgiving if people want to use
     things that don't start with "cros/". Instead, we only enforce that
     people use tags if they want to use the one-argument version of
     cros_changelog.
  2. Tags are quoted in the command-line so that people can, for instance,
     diff 'cros/master{2 days ago}' vs 'cros/master{1 day ago}'.

Change-Id: I28c7d77ae83256d4c28411ef589f3e726cc81d80

BUG=chromium-os:8205
TEST=Ran ( ./cros_changelog 0.9.104.0 cros/master > /tmp/test1.html &&
          ./cros_changelog --sort-by-date 0.9.104.0 cros/master > /tmp/test2.html )
    Both commands print changes between 0.9.104.0 and master, but the second command prints results sorted by date.

Committed: http://chrome-svn/viewvc/chromeos?view=rev&revision=6ceddf0

[diandersAtChromium, 2010-10-28 20:44:07]

LGTM

http://codereview.chromium.org/4130009/diff/1/2
File chromite/bin/cros_changelog (right):

http://codereview.chromium.org/4130009/diff/1/2#newcode194
chromite/bin/cros_changelog:194: changes.sort(key=lambda x: x.commit_date)
...or key=operator.attrgetter("commit_date")