It happens that closing file descriptor fails whereas the blob is
perfectly readable.  According to perlman the reasons could be:

   If the file handle came from a piped open, "close" will additionally
   return false if one of the other system calls involved fails, or if the
   program exits with non-zero status.  (If the only problem was that the
   program exited non-zero, $! will be set to 0.)  Closing a pipe also waits
   for the process executing on the pipe to complete, in case you want to
   look at the output of the pipe afterwards, and implicitly puts the exit
   status value of that command into $?.

   Prematurely closing the read end of a pipe (i.e. before the process writ-
   ing to it at the other end has closed it) will result in a SIGPIPE being
   delivered to the writer.  If the other end can't handle that, be sure to
   read all the data before closing the pipe.

In this case we don't mind that close fails.
Signed-off-by: NSylvain Rabot <sylvain@abstraction.fr>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>