Merge branch 'js/prep-symlink-windows' into jch

Further preparation to upstream symbolic link support on Windows.

* js/prep-symlink-windows:
  trim_last_path_component(): avoid hard-coding the directory separator
  strbuf_readlink(): support link targets that exceed PATH_MAX
  strbuf_readlink(): avoid calling `readlink()` twice in corner-cases
  init: do parse _all_ core.* settings early
  mingw: do resolve symlinks in `getcwd()`

diff --cc environment.h
Simple merge

diff --cc setup.c
Simple merge

diff --cc strbuf.c
Simple merge