[rfc] bzr-colo into core

[Nicholas Allen]

>
> People working on large trees really want to have just one on-disk
> checkout at a time, so they don't use too much disk space and so they
> don't waste time building a new tree just to start a new branch.  
I diagree completely. If you have a large tree or use a compiled
language like C++ colocated branches are almost definitely what you
don't want. You need multiple working trees so that you don't have to
rebuild each time you switch a branch. If there's only one tree then
when you switch the whole project will likely have to be recompiled
again (especially if a common header file is modified because of the
switch). This would be unacceptable for me.

There's also something elegant about the simplicity of 1 directory = 1
branch that I think gets lost like this. It's always clear to me which
branch I'm working on when they are in separate directories.

As long as it's just as easy to have a single branch in a directory with
multiple trees and all the workflows that Bazaar currently supports then
I don't mind.

As for the disk space argument - I seriously can't believe that that is
considered an advantage. Disk space even for huge projects is no problem
nowadays.

I think colo could replace the idea of lightweight checkouts and make
that simpler but in general I think I wouldn't use it much.

NIck