Change resolve_symlink() to take a strbuf rather than a string as
parameter. This simplifies the code and removes an arbitrary pathname
length restriction. It also means that lock_file's filename field no
longer needs to be initialized to a large size.
Helped-by: Torsten Bögershausen <tboegi@web.de> Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>