xstow version 1.0.1
In configure.ac a rule is defined
if test $support_format -gt 0 ; then support_format=yes else support_format=no fi
and so this is present in the configure script
if test $support_format -gt 0
But support_format is never intialized (tested on Linux Mint 16 i686 and Debian 7.4 armv7l) and thus on running configure the following error is displayed because Bourne shell or Bash is trying to do test on an unset bariable and thus on a non numeric value.
checking create merge-info?... enabled /usr/src/build/xstow-1.0.1/configure: line 6038: test: -gt: unary operator expected configure: creating ./config.status