remote-bzr: access branches only when needed

Bazaar doesn't seem to be tested for multiple usage of branches, so
resources seem to be leaked all over. Let's try to minimize this by
accessing the Branch objects only when needed.

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

contrib/remote-helpers/git-remote-bzr

@@ -277,7 +277,7 @@ def export_branch(repo, name):
     ref = '%s/heads/%s' % (prefix, name)
     tip = marks.get_tip(name)
 
-    branch = branches[name]
+    branch = bzrlib.branch.Branch.open(branches[name])
     repo = branch.repository
 
     branch.lock_read()
@@ -582,7 +582,7 @@ def parse_commit(parser):
 
     if ref.startswith('refs/heads/'):
         name = ref[len('refs/heads/'):]
-        branch = branches[name]
+        branch = bzrlib.branch.Branch.open(branches[name])
     else:
         die('unknown ref')
 
@@ -683,7 +683,7 @@ def do_export(parser):
 
     for ref, revid in parsed_refs.iteritems():
         name = ref[len('refs/heads/'):]
-        branch = branches[name]
+        branch = bzrlib.branch.Branch.open(branches[name])
         branch.generate_revision_history(revid, marks.get_tip(name))
 
         if name in peers:
@@ -733,7 +733,7 @@ def do_list(parser):
             master_branch = name
         print "? refs/heads/%s" % name
 
-    branch = branches[master_branch]
+    branch = bzrlib.branch.Branch.open(branches[master_branch])
     branch.lock_read()
     for tag, revid in branch.tags.get_tag_dict().items():
         try:
@@ -822,13 +822,15 @@ def get_repo(url, alias):
         # branch
 
         name = 'master'
-        branch = origin.open_branch()
+        remote_branch = origin.open_branch()
 
         if not is_local:
-            peers[name] = branch.base
-            branches[name] = get_remote_branch(origin, branch, name)
+            peers[name] = remote_branch.base
+            branch = get_remote_branch(origin, remote_branch, name)
         else:
-            branches[name] = branch
+            branch = remote_branch
+
+        branches[name] = branch.base
 
         return branch.repository
     else:
@@ -838,13 +840,15 @@ def get_repo(url, alias):
         # stupid python
         wanted = [e for e in wanted if e]
 
-        for name, branch in find_branches(repo, wanted):
+        for name, remote_branch in find_branches(repo, wanted):
 
             if not is_local:
-                peers[name] = branch.base
-                branches[name] = get_remote_branch(origin, branch, name)
+                peers[name] = remote_branch.base
+                branch = get_remote_branch(origin, remote_branch, name)
             else:
-                branches[name] = branch
+                branch = remote_branch
+
+            branches[name] = branch.base
 
         return repo