[RFC] proposed changes to log UI

[Ian Clatworthy]

As currently implemented, log is O(history). I'd like
to make some UI changes so that it can be refactored
to use a more intelligent approach by default for
common operations.

1. If a single revision is given, I just want to log it,
   not all the revisions merging it to mainline. If you
   want the latter, perhaps -v ought to be required?

2. I want to make --short the default format. (Many of us
   do this already as it provides the best signal:noise
   ratio and performance for most of the workflows that
   Bazaar encourages.)

3. If a revision range is given and the log format only
   supports mainline revisions, I don't want to check that
   the revisions are on the mainline by default. This check
   is O(history) and, IMO, ought to only be done if a
   new option (--strict say) is specified.

Thoughts?

Ian C.