t/unit-tests/clar: fix -Wmaybe-uninitialized with -Og

When building with -Og on gcc 15.1.1, the build produces a warning. In
practice, though, this cannot be hit because `exact` acts as a guard and
that variable can only be set after `matchlen` is already initialized

Assign a default value to `matchlen` so that the warning is silenced.

Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

0 files changed, 0 insertions, 0 deletions