bzr branches is comically slow on a remote repository

[Glyph Lefkowitz]

This is just ridiculous:

glyph@vetinari:~/Projects/Twisted/mirror$ time bzr branches bzr+ssh://svn.twistedmatrix.com/var/www/bzr/Twisted > branchlist
  2063kB 2kB/s /
real 12m16.855s
user 0m11.781s
sys 0m0.496s
glyph@vetinari:~/Projects/Twisted/mirror$ time ssh svn.twistedmatrix.com bzr branches /var/www/bzr/Twisted > branchlist.2

real 0m5.898s
user 0m0.012s
sys 0m0.012s
glyph@vetinari:~/Projects/Twisted/mirror$ diff branchlist branchlist.2
glyph@vetinari:~/Projects/Twisted/mirror$ wc -l branchlist
278 branchlist

What on earth is it doing?

[Aaron Bentley (abentley)]

It is looking for branches by doing low-level operations such listing directories and opening files, because Bazaar's BzrDir.find_branches method isn't optimized for remote operations.

[Jelmer Vernooij (jelmer)]

BzrDir.find_branches should be deprecated because it is used as a classmethod method that can't be overriden.

the "bzr branches" command in bzr 2.5 uses the "BzrDir.list_branches" method, which /can/ be overridden (and bzr-svn does so).