Bug#1072743: pdfxup: --pages option fails if page range omits start or end of range

["Sanjoy Mahajan" <sanjoy@mit.edu>]

Dear Nicolas,

I found a small bug in the TL pdfxup (on Debian) and filed a Debian bug
report.  The Debian TL maintainers suggested that I discuss it with you
as upstream, as the bug is likely upstream.

The bug report is in the Debian BTS:
<https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1072743>

But here is a copy of that report:

The man entry for pdfxup says that --pages can handle an omitted start
or end of range, e.g. "--pages 2-" or "--pages -5".  However, using the
following pdf file as a test (it's one page long) gives an error
if either the start or end of the range is omitted.

Omitting the end of the range:

$ pdfxup --pages 1- /usr/share/cups/data/default-testpage.pdf
-> processing options 
/usr/bin/pdfxup: line 405: [[: 1-: syntax error: operand expected (error token is "-")
   /usr/share/cups/data/default-testpage.pdf has 1 page(s); pages 1- do not exist.
/usr/bin/pdfxup: line 405: [[: 1-: syntax error: operand expected (error token is "-")
   /usr/share/cups/data/default-testpage.pdf has 1 page(s); pages 1- do not exist.
   No pages to include. Aborting.

Omitting the start of the range also fails:

$ pdfxup --pages -1 /usr/share/cups/data/default-testpage.pdf
Error: option '--pages' expects a range, not '-1'.
Aborting.

But omitting both start and end works as described in the man page:

$ pdfxup --pages - /usr/share/cups/data/default-testpage.pdf
-> processing options 
-> computing bounding box.
-> producing final file 
   final scale: 95.35675%
-> cleaning 


I am happy to test any patches.

Best regards,
-Sanjoy