bookmarks: drop always-None argument from calculateupdate()

Thanks to Yuya for noticing.

Differential Revision: https://phab.mercurial-scm.org/D3135

mercurial/bookmarks.py

@@ -348,11 +348,10 b' def headsforactive(repo):'
             heads.append(n)
     return heads
 
-def calculateupdate(ui, repo, checkout):
+def calculateupdate(ui, repo):
     '''Return a tuple (activemark, movemarkfrom) indicating the active bookmark
     and where to move the active bookmark from, if needed.'''
-    movemarkfrom = None
-    if checkout is None:
+    checkout, movemarkfrom = None, None
         activemark = repo._activebookmark
         if isactivewdirparent(repo):
             movemarkfrom = repo['.'].node()

mercurial/destutil.py

@@ -56,7 +56,7 b' def _destupdatebook(repo, clean):'
     """decide on an update destination from active bookmark"""
     # we also move the active bookmark, if any
     node = None
-    activemark, movemark = bookmarks.calculateupdate(repo.ui, repo, None)
+    activemark, movemark = bookmarks.calculateupdate(repo.ui, repo)
     if activemark is not None:
         node = repo.lookup(activemark)
     return node, movemark, activemark