remote-bzr: add option to specify branches

We might not want all the branches. And branch handling in bazaar is
rather tricky, so it's safer to simply specify them.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Felipe Contreras

contrib/remote-helpers/git-remote-bzr

@@ -13,6 +13,9 @@
 # or
 # % git clone bzr::lp:myrepo
 #
+# If you want to specify which branches you want track (per repo):
+# git config remote-bzr.branches 'trunk, devel, test'
+#
 
 import sys
 
@@ -51,6 +54,12 @@ def warn(msg, *args):
 def gittz(tz):
     return '%+03d%02d' % (tz / 3600, tz % 3600 / 60)
 
+def get_config(config):
+    cmd = ['git', 'config', '--get', config]
+    process = subprocess.Popen(cmd, stdout=subprocess.PIPE)
+    output, _ = process.communicate()
+    return output
+
 class Marks:
 
     def __init__(self, path):
@@ -756,7 +765,7 @@ def get_remote_branch(origin, remote_branch, name):
 
     return branch
 
-def find_branches(repo):
+def find_branches(repo, wanted):
     transport = repo.user_transport
 
     for fn in transport.iter_files_recursive():
@@ -767,6 +776,9 @@ def find_branches(repo):
         name = name if name != '' else 'master'
         name = name.replace('/', '+')
 
+        if wanted and not name in wanted:
+            continue
+
         try:
             cur = transport.clone(subdir)
             branch = bzrlib.branch.Branch.open_from_transport(cur)
@@ -815,7 +827,11 @@ def get_repo(url, alias):
     else:
         # repository
 
-        for name, branch in find_branches(repo):
+        wanted = get_config('remote-bzr.branches').rstrip().split(', ')
+        # stupid python
+        wanted = [e for e in wanted if e]
+
+        for name, branch in find_branches(repo, wanted):
 
             if not is_local:
                 peers[name] = branch