remote-bzr: avoid bad refs

Versions of fast-export before v1.8.2 throws a bad 'reset' commands
because of a behavior in transport-helper that is not even needed.
We should ignore them, otherwise we will treat them as branches and
fail.

This was fixed in v1.8.2, but some people use this script in older
versions of git.

Also, check if the ref was a tag, and skip it for now.

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

contrib/remote-helpers/git-remote-bzr

@@ -682,6 +682,7 @@ def do_export(parser):
             die('unhandled export command: %s' % line)
 
     for ref, revid in parsed_refs.iteritems():
+        if ref.startswith('refs/heads/'):
             name = ref[len('refs/heads/'):]
             branch = bzrlib.branch.Branch.open(branches[name])
             branch.generate_revision_history(revid, marks.get_tip(name))
@@ -699,6 +700,13 @@ def do_export(parser):
                 wt.update()
             except bzrlib.errors.NoWorkingTree:
                 pass
+        elif ref.startswith('refs/tags/'):
+            # TODO: implement tag push
+            print "error %s pushing tags not supported" % ref
+            continue
+        else:
+            # transport-helper/fast-export bugs
+            continue
 
         print "ok %s" % ref