bookmarks: calculateupdate() returns a bookmark, not a rev

This changes the inaccurate/unclear documentation and also changes the
code so "node" now contains a binary nodeid.

Differential Revision: https://phab.mercurial-scm.org/D3087

mercurial/bookmarks.py

@@ -349,8 +349,8 b' def headsforactive(repo):'
     return heads
 
 def calculateupdate(ui, repo, checkout):
-    '''Return a tuple (targetrev, movemarkfrom) indicating the rev to
-    check out and where to move the active bookmark from, if needed.'''
+    '''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:
         activemark = repo._activebookmark

mercurial/destutil.py

@@ -55,10 +55,10 b' def _destupdateobs(repo, clean):'
 def _destupdatebook(repo, clean):
     """decide on an update destination from active bookmark"""
     # we also move the active bookmark, if any
-    activemark = None
-    node, movemark = bookmarks.calculateupdate(repo.ui, repo, None)
-    if node is not None:
-        activemark = node
+    node = None
+    activemark, movemark = bookmarks.calculateupdate(repo.ui, repo, None)
+    if activemark is not None:
+        node = repo.lookup(activemark)
     return node, movemark, activemark
 
 def _destupdatebranch(repo, clean):