bzr upgrade extended explanation

[Alexey Balmashnov]

Is there a documentation somewhere explaining what one may expect
after upgrade of branch?

I mean something with answers to questions like:
* How upgrade of repository is performed (does one need to upgrade
every branch)?
* How upgrade actions may/will influence other users, e.g. checkout
branches, branches having different format?
* How safe is to change a format
...

bzr help upgrade positions itself to be relevant only for branches:
---
$ bzr help upgrade
Purpose: Upgrade branch storage to current format.
---
Although, there are some explanations involving repositories in the
format specific sections of help output.

Digging through the website I did not find useful information.


Thanks,
  Alexey