Code review comment for lp:~parthm/bzr/538868-message-for-heavy-checkout

I realise this has gone through, so I'd like to just request some more
stuff if you have time; if not please file a bug.

The message will show up when doing a heavy checking in a repository;
that's just annoying - no history is being copied, so no message
should appear. Recommended fix: move the notification into the core,
out of builtins.py.

Secondly, if its worth telling people we're copying [a lot] of history
for checkout, I think its worth telling them about it for branch and
merge too. Perhaps lets set some sort of heuristic (e.g. 100 or more
revisions) and have the warning trigger on that?

-Rob