with: use context manager for transaction in strip

mercurial/repair.py

@@ -160,10 +160,10 b' def strip(ui, repo, nodelist, backup=Tru'
         msg = _('programming error: cannot strip from inside a transaction')
         raise error.Abort(msg, hint=_('contact your extension maintainer'))
 
-    tr = repo.transaction("strip")
+    try:
+        with repo.transaction("strip") as tr:
     offset = len(tr.entries)
 
-    try:
         tr.startgroup()
         cl.strip(striprev, tr)
         mfst.strip(striprev, tr)
@@ -171,15 +171,11 b' def strip(ui, repo, nodelist, backup=Tru'
             repo.file(fn).strip(striprev, tr)
         tr.endgroup()
 
-        try:
             for i in xrange(offset, len(tr.entries)):
                 file, troffset, ignore = tr.entries[i]
                 repo.svfs(file, 'a').truncate(troffset)
                 if troffset == 0:
                     repo.store.markremoved(file)
-            tr.close()
-        finally:
-            tr.release()
 
         if saveheads or savebases:
             ui.note(_("adding branch\n"))