bzr version-info should use branch nick from last committed revision

[Alexander Belchenko]

Currently output of `bzr version-info` command shows current branch nick. It should use committed in last revision branch nick, otherwise when I'm changing directories or change the nick manually I'm get different results every time. It's wrong.

C:\Temp>bzr init a
Created a standalone tree (format: pack-0.92)

C:\Temp\a>bzr ci -m test --unchanged
Committing to: C:/Temp/a/
Committed revision 1.

C:\Temp\a>bzr version-info
revision-id: <email address hidden>
date: 2009-03-30 16:14:38 +0300
build-date: 2009-03-30 16:14:44 +0300
revno: 1
branch-nick: a

C:\Temp\a>bzr nick b

C:\Temp\a>bzr version-info
revision-id: <email address hidden>
date: 2009-03-30 16:14:38 +0300
build-date: 2009-03-30 16:15:03 +0300
revno: 1
branch-nick: b

At least user should have the control over this value: either use current nick, or use the committed value. Current behavior is bad for auto-build or auto-test systems that use or rely on version-info output.