Issues with hg update -C and bookmarks

[Marc Strapetz]

With the following setup:

$ hg init
$ touch x
$ hg commit -A "initial import"
$ touch y
$ hg commit -A -m "y added"
$ hg checkout 0
$ touch z
$ hg commit -A -m "z added"
$ hg up 1
$ hg bookmark bm

There will be default with two diverged heads at r1 and r2 and a 
bookmark on r1.

$ hg summary
parent: 1:4009599f6088
  y added
branch: default
bookmarks: *bm
...

Starting from this setup, following behavior is rather unexpected to me:

(1) hg update -C . will loose the active bookmark

$ hg update -C .
$ hg summary
parent: 1:4009599f6088
  y added
branch: default
bookmarks: bm
commit: (clean)
update: 1 new changesets, 2 branch heads (merge)

I would expect to see bookmark "*bm" still active.

(2) hg upgdate -C checks out r2 (expected), but leaves bookmark bm 
active (unexpected)

$ hg update -C
$ hg summary
parent: 2:eb990d6c7e06 tip
  z added
branch: default
commit: (clean)
update: 1 new changesets, 2 branch heads (merge)

$ hg bookmarks
  * bm                        1:4009599f6088

I would probably expect that bookmark "bm" isn't active anymore. What's 
the meaning of an active bookmark which is not checked out?

Tested on Windows with Mercurial 3.4.2.

-Marc