In the fetch_index implementations in http-push.c and http-walker.c,
the string returned by sha1_to_hex is assumed to stay immutable.
This patch ensures that hex stays immutable by copying the string
returned by sha1_to_hex (via xstrdup) and frees it subsequently. It
also refactors free()'s and fclose()'s with labels.
Signed-off-by: Tay Ray Chuan <rctay89@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>