bookmarks: refactor in preparation for next commit

Differential Revision: https://phab.mercurial-scm.org/D8116

mercurial/bookmarks.py

@@ -463,6 +463,10 b' def update(repo, parents, node):'
     return bool(bmchanges)
 
 
+def isdivergent(b):
+    return b'@' in b and not b.endswith(b'@')
+
+
 def listbinbookmarks(repo):
     # We may try to list bookmarks on a repo type that does not
     # support it (e.g., statichttprepository).
@@ -471,7 +475,7 b' def listbinbookmarks(repo):'
     hasnode = repo.changelog.hasnode
     for k, v in pycompat.iteritems(marks):
         # don't expose local divergent bookmarks
-        if hasnode(v) and (b'@' not in k or k.endswith(b'@')):
+        if hasnode(v) and not isdivergent(k):
             yield k, v