Merge branch 'nd/root-git'

Merge branch 'nd/root-git'

* nd/root-git:
  Add test for using Git at root of file system
  Support working directory located at root
  Move offset_1st_component() to path.c
  init-db, rev-parse --git-dir: do not append redundant slash
  make_absolute_path(): Do not append redundant slash

Conflicts:
	setup.c
	sha1_file.c