[RFC] Update should mention WHAT it is up to date with

[Neil Martinsen-Burrell]

There have been a sequence of bugs arising from the fact that ``bzr 
update`` is a legitimate command in a branch with its own working tree, 
but often it doesn't do what users want.  What people often want is to 
get their branch "up to date" with some other branch and they should be 
using ``bzr pull`` or ``bzr merge`` to do so.  I run into the situation 
when using bound branches that I often unbind for offline commits. 
Then, when unbound, ``bzr up`` is a successful no-op, but what I *meant* 
is to make this branch up to date with the branch it was bound to.

I've wanted for a while to address this by using the message: "Up to 
date at revision x of branch y" and I have a branch of bzr that does 
that, but it causes lots of test failures (understandably) and before I 
go fixing all of them, I wanted to hear some feedback.

Do people feel that this will address the issue with update being not 
what people want, by informing them that their working tree is up to 
date with its (local) branch?  Is it otherwise useful (e.g. for those 
using switch a lot)?

Implementation questions:

Is there a bzrlib function to take a branch.base URL and shorten it (for 
example, file:/// URLs could have the URL prefix removed)?  Should we 
try to use "." in the shortened form if possible?

For tests that have very long and varying branch names, should I just 
change assertEndsWith("Up to date at revision 1\n") to an appropriate 
assertContainsRe?

-Neil