The value returned by getenv() is not guaranteed to remain valid across
other environment function calls. But in between our call and using the
value, we run fill_textconv(), which may do quite a bit of work,
including spawning sub-processes.
We can make this safer by calling getenv() right before we actually look
at its value.
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>