When "git bundle" aborts due to an empty commit ranges
(i.e. resulting in an empty pack), it left a file descriptor to an
lockfile open, which resulted in leftover lockfile on Windows where
you cannot remove a file with an open file descriptor.  This has
been corrected.

* jk/close-duped-fd-before-unlock-for-bundle:
  bundle: dup() output descriptor closer to point-of-use