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Spurious 'grep: writing output' in Cygwin 1.7.5-1 in certain cases

We are seeing grep emit 'grep: writing output' multiple times in
certain cases where the output of grep is piped to another program.
Specifically, we see it in the following cases:

  grep thisandthat foo.txt | head
  grep thisandthat foo.txt | less

In the latter case the 'grep: writing output' messages do not appear
until pressing Q to quit less.

There appear to be two 'grep: writing output' messages for each
line grepped.

Not all pipe operations exhibit this behavior. For example with the
same file, we do not see it in either of these cases:

  grep thisandthat foo.txt | last
  grep thisandthat foo.txt | wc

Moreover a non-piped grep does not exhibit this behavior:

  grep thisandthat foo.txt

Nor do we see it if the output of grep is redirected:

  grep thisandthat foo.txt > out.txt

Note: in this case 'grep: writing output' does not appear in
out.txt; my guess is that they are being sent to STDERR when they
do occur.

  - Matthew Kidd

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