hgweb: extract a generator function of _siblings class

_siblings will be converted to a plain function.

mercurial/hgweb/webutil.py

@@ -181,16 +181,10 b' class filerevnav(revnav):'
     def hex(self, rev):
         return hex(self._changelog.node(self._revlog.linkrev(rev)))
 
-class _siblings(object):
-    def __init__(self, siblings=None, hiderev=None):
-        if siblings is None:
-            siblings = []
-        self.siblings = [s for s in siblings if s.node() != nullid]
-        if len(self.siblings) == 1 and self.siblings[0].rev() == hiderev:
-            self.siblings = []
-
-    def __iter__(self):
-        for s in self.siblings:
+# TODO: maybe this can be a wrapper class for changectx/filectx list, which
+# yields {'ctx': ctx}
+def _ctxsgen(ctxs):
+    for s in ctxs:
             d = {
                 'node': s.hex(),
                 'rev': s.rev(),
@@ -203,6 +197,17 b' class _siblings(object):'
                 d['file'] = s.path()
             yield d
 
+class _siblings(object):
+    def __init__(self, siblings=None, hiderev=None):
+        if siblings is None:
+            siblings = []
+        self.siblings = [s for s in siblings if s.node() != nullid]
+        if len(self.siblings) == 1 and self.siblings[0].rev() == hiderev:
+            self.siblings = []
+
+    def __iter__(self):
+        return _ctxsgen(self.siblings)
+
     def __len__(self):
         return len(self.siblings)