strip: move attributes shortcut assigned earlier

This series will add support for "soft" stripping using the archived phase in
addition to the usual heavy weight revlog stripping. First, we need to
refactor the strip function to extract logic common to the "soft-strip" case.

We are about to extract bits of the strip function into separate functions.
Those blocks of code contain variables for frequently accessed attributes. We
move those variables outside of the soon to be moved blocks.

mercurial/repair.py

@@ -108,8 +108,9 b' def strip(ui, repo, nodelist, backup=Tru'
 
     repo = repo.unfiltered()
     repo.destroying()
+    vfs = repo.vfs
+    cl = repo.changelog
 
-    cl = repo.changelog
     # TODO handle undo of merge sets
     if isinstance(nodelist, str):
         nodelist = [nodelist]
@@ -169,7 +170,6 b' def strip(ui, repo, nodelist, backup=Tru'
 
     # create a changegroup for all the branches we need to keep
     backupfile = None
-    vfs = repo.vfs
     node = nodelist[-1]
     if backup:
         backupfile = backupbundle(repo, stripbases, cl.heads(), node, topic)