Revert "hg2git: Replaces space with "_" in branches name"

The get_branch() function's purpose is to detect whether a mercurial
branch name actually should be considered the default branch.

Sanitizing branch and tag names for git is done in sanitize_name().

Noted by Jonathan Nieder.

This reverts commit cdfdae36c8.

hg2git.py

@@ -49,7 +49,7 @@ def get_branch(name):
   # other CVS imports may need it, too
   if name=='HEAD' or name=='default' or name=='':
     name=cfg_master
-  return name.replace(' ', '_')
+  return name
 
 def get_changeset(ui,repo,revision,authors={}):
   node=repo.lookup(revision)