manual: Improve documentation of --output.

The three redirection features of --output are useless for select
mode since these redirections can also be created by the shell.

This commit adds a paragraph which clarifies this. We use the
opportunity to reword the remaining text for the option slightly.

diff --git a/select.ggo b/select.ggo
index d96609536e46865dd6134a918e185103e5c0c6ff..d7f8c9388b3ac4d6509cb5e7e0719079b65feba7 100644 (file)
--- a/select.ggo
+++ b/select.ggo
@@ -134,28 +134,32 @@ string typestr="path"
 optional
 default="-"
 details="
-       If empty, or not given, use stdout. The following conventions
-       cause the output to be written differently:
-
-       An output file name of \"-\" means stdout.
-
-       \"path\" may be prepended by '>' which instructs adu to
-       truncate the output file to length zero.  If \"path\" does
-       not start with '>' and \"path\" already exists, the select
-       query is being aborted. Otherwise, \"path\" is created and
-       output is written to \"path\".
-
-       If the first two characters of \"path\" are '>', the output
-       file (given by removing the leading \">>\" from \"path\")
-       is being opened in append mode. It is no error if the output
-       file does not exist but, as above, the output file name \">>\"
-       is considered invalid.
-
-       If the first character of \"path\" is '|', a pipe is created
-       and the rest of \"path\" is being executed with its standard in
-       redirected to the reading end of the pipe. The output of adu
-       is written to the writing end of the pipe. Again, specifying
-       only \"|\" is considered invalid and causes an error.
+       This option is only useful in interactive mode. If stdin is redirected
+       from a script, and the script contains several queries one can use
+       this option to let each query write its output to a different file.
+
+       If the option is not given, or its argument is either \"-\" or the
+       empty string, stdout is assumed. The following conventions cause the
+       output to be written in a different way:
+
+       \"path\" may be prepended by '>' which instructs adu to truncate
+       the output file to length zero. If \"path\" does not start with
+       '>' and \"path\" already exists, the query is aborted. Otherwise,
+       the file is created and truncated. The output file name \">\" is
+       considered invalid.
+
+       If the first two characters of \"path\" are '>', the output file
+       (given by removing the leading \">>\" from \"path\") is opened in
+       append mode. It is no error if the output file does not exist. However,
+       as above the output file name \">>\" is considered invalid.
+
+       If the first character of \"path\" is '|', a pipe is created and the
+       rest of \"path\" is executed with stdin redirected to the reading
+       end of the pipe while the query output is written to the writing end
+       of the pipe. Again, specifying only \"|\" is considered invalid and
+       causes an error.
+
+       See the manual page for examples.
 "
 
 option "user-summary-sort" -