Hg Pull vs. Update to branch tip

Using开发者_如何学Go TortoiseHg Synchronize, clicking "Pull" pulls down the 2nd most recent revision.

At the bottom of the Synchronize interface is a button, "Update to branch tip." Clicking this button pulls down the most recent revision.

What is happening here?

Command line hg tells this:

$ hg help pull

...

Pull changes from a remote repository to a local one.

...

-R is specified). By default, this does not update the copy of the
project in the working directory.

vs.

$ hg help up

...

Update the repository's working directory to the specified revision, or the tip of the current branch if none is specified.

If you are new to mercurial or want to know you havent missed any options, this is could be helpful:

http://blog.hanxiaogang.com/hg-guide/