taler-exchange-offline(1): document ‘show -’; add example variant

This is the result of email discussion 2021-01-05.

1 files changed, 9 insertions, 0 deletions

diff --git a/manpages/taler-exchange-offline.1.rst b/manpages/taler-exchange-offline.1.rst
index 793a00fc..1c901b8c 100644
--- a/manpages/taler-exchange-offline.1.rst
+++ b/manpages/taler-exchange-offline.1.rst
@@ -116,6 +116,9 @@ other parameters.
 
 It consumes the output of the ``download`` subcommand, either from ``stdin`` or
 directly.
+However, if given arg ``-`` (hyphen), this input is not consumed,
+but instead is passed to the next command.  This functions like the
+tee(1) command.
 
 Its output always goes to ``stdout`` for human consumption (not in JSON).  It
 is usually a bad idea (but possible) to combine ``show`` with other subcommands,
@@ -323,6 +326,12 @@ Note that doing this is only recommended in non-production deployments.
 
    $ taler-exchange-offline download sign upload
 
+Here is a variant that shows the output of ``download``, but does not consume it,
+so that ``sign`` can see it as input, as in the variant without ``show``.
+
+.. code-block:: console
+
+   $ taler-exchange-offline download show - sign upload
 
 Create signature to enable bank account (offline)
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