rebase: replace extrafn field with _makeextrafn invocations

As per Yuya's advice, we would like to slightly reduce the amount of state
which is stored in rebaseruntime class. In this case, we don't need to store
extrafn field, as we can produce the necessary value by calling _makeextrafn
and the perf overhead is negligible.

hgext/rebase.py

@@ -148,7 +148,6 b' class rebaseruntime(object):'
         self.extrafns = [_savegraft]
         if e:
             self.extrafns = [e]
-        self.extrafn = None
 
         self.keepf = opts.get('keep', False)
         self.keepbranchesf = opts.get('keepbranches', False)
@@ -336,8 +335,6 b' class rebaseruntime(object):'
         if self.activebookmark:
             bookmarks.deactivate(repo)
 
-        self.extrafn = _makeextrafn(self.extrafns)
-
         self.sortedstate = sorted(self.state)
         total = len(self.sortedstate)
         pos = 0
@@ -381,7 +378,7 b' class rebaseruntime(object):'
                     editform = cmdutil.mergeeditform(merging, 'rebase')
                     editor = cmdutil.getcommiteditor(editform=editform, **opts)
                     newnode = concludenode(repo, rev, p1, p2,
-                                           extrafn=self.extrafn,
+                                           extrafn=_makeextrafn(self.extrafns),
                                            editor=editor,
                                            keepbranches=self.keepbranchesf,
                                            date=self.date)
@@ -444,7 +441,8 b' class rebaseruntime(object):'
             revtoreuse = self.sortedstate[-1]
             newnode = concludenode(repo, revtoreuse, p1, self.external,
                                    commitmsg=commitmsg,
-                                   extrafn=self.extrafn, editor=editor,
+                                   extrafn=_makeextrafn(self.extrafns),
+                                   editor=editor,
                                    keepbranches=self.keepbranchesf,
                                    date=self.date)
             if newnode is None: