am: drop "dir" parameter from am_state_init
The only caller of this function passes in a static buffer
returned from git_path(). This looks dangerous at first
glance, but turns out to be OK because the first thing we do
is xstrdup() the result.
Let's turn this into a git_pathdup(). That's slightly more
efficient (no extra copy), and makes it easier to audit for
dangerous git_path() invocations.
Since there's only a single caller, let's just set this
default path inside the init function. That makes the memory
ownership clear.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>