bzr heads help

[David Muir]

Two issues:

1. I noticed that running bzr heads --all on a relatively small
repository (~1800 revs) takes quite a long time:

$ bzr heads --all --debug-time
get heads: 0.134533882141
make head marks: 79.3243851662

Fetching just the live heads takes just as long.
Is it supposed to be that slow?

2. What is the difference between live and dead heads? My guess is that
a live head is one that exists in a branch, but has not been merged into
any other branch?

eg :

branch1 - live head
A-B-C-D-E

trunk - dead head?
A-B-C

after branch1 has been merged into trunk:

branch1 - dead head
A-B-C-D-E

trunk - live head
A-B-C-----F
     \D-E/
      

Is this correct?

Cheers,
David