shelve: move unshelve-finishing logic to a separate function

shelve: move unshelve-finishing logic to a separate function

Finishing unshelve involves two steps now:
- stripping a changelog
- aborting a transaction
Obs-based shelve will not require these things, so isolating this logic
into a separate function where the normal/obs-shelve branching is
going to be implemented seems to be like a nice idea.

Behavior-wise this change moves 'unshelvecleanup' from being between
changelog stripping and transaction abortion to being after them.
I don't think this has any negative effects.

--- a/hgext/shelve.py	Thu Nov 10 11:02:39 2016 -0800
+++ b/hgext/shelve.py	Fri Nov 11 07:01:27 2016 -0800
@@ -707,6 +707,14 @@
     toforget = (addedafter & shelveunknown) - addedbefore
     repo[None].forget(toforget)
 
+def _finishunshelve(repo, oldtiprev, tr):
+    # The transaction aborting will strip all the commits for us,
+    # but it doesn't update the inmemory structures, so addchangegroup
+    # hooks still fire and try to operate on the missing commits.
+    # Clean up manually to prevent this.
+    repo.unfiltered().changelog.strip(oldtiprev, tr)
+    _aborttransaction(repo)
+
 @command('unshelve',
          [('a', 'abort', None,
            _('abort an incomplete unshelve operation')),
@@ -846,16 +854,8 @@
         _forgetunknownfiles(repo, shelvectx, addedbefore)
 
         shelvedstate.clear(repo)
-
-        # The transaction aborting will strip all the commits for us,
-        # but it doesn't update the inmemory structures, so addchangegroup
-        # hooks still fire and try to operate on the missing commits.
-        # Clean up manually to prevent this.
-        repo.unfiltered().changelog.strip(oldtiprev, tr)
-
+        _finishunshelve(repo, oldtiprev, tr)
         unshelvecleanup(ui, repo, basename, opts)
-
-        _aborttransaction(repo)
     finally:
         ui.quiet = oldquiet
         if tr: