[MERGE/RFC] Warn the user when updating with local commits, uncommited changes, and master branch changes (#113809)

[Jelmer Vernooij]

Jelmer Vernooij has voted resubmit.
Status is now: Resubmit
Comment:
this needs a test and the indentation seems wrong (non-PEP8)

For details, see: 
http://bundlebuggy.aaronbentley.com/project/bzr/request/%3C2050840047.12782221229197485802.JavaMail.root%40mail-2.01.com%3E
Project: Bazaar