t0614: use numerical comparison with test_line_count

t0614: use numerical comparison with test_line_count

In this comparison, we want to know whether the number of lines is
greater than 1.  Our test_line_count function passes the first argument
as the comparison operator to test, so what we want is a numerical
comparison, not a string comparison.  While this does not produce a
functional problem now, it could very well if we expected two or more
items, in which case the value "10" would not match when it should.

Furthermore, the "<" and ">" comparisons are new in POSIX 1003.1-2024
and we don't want to require such a new version of POSIX since many
popular and supported operating systems were released before that
version of POSIX was released.

Finally, zsh's builtin test operator does not like the greater-than sign
in "test", since it is only supported in the double-bracket extension.
This has been reported and will be addressed in a future version, but
since our code is also technically incorrect, as well as not very
compatible, let's fix it by using a numeric comparison.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>