How do I do what svn switch
does, in Mercurial?
That is change my working directory to switch to another branch in the repository?
Alternate answer, in case by "branch" you mean "another clone of the repo that lives in some arbitrary location on the net": you can't.
In other words, given a repo at hg.a.com, and a clone of that repo hg.b.com, there is no command like
hg switch hg.b.com .
(using svn parlance there, assuming your current directory is the root of a clone of hg.a.com).
However, you can clone hg.a.com, locally clone that clone (which should be relatively inexpensive), and then pull from hg.b.com to pick up any additional changes that might live there.