Merge branch 'maint'

Merge branch 'maint'

* maint:
  Start 1.6.0.2 maintenance cycle
  tests: use "git xyzzy" form (t7200 - t9001)
  tests: use "git xyzzy" form (t7000 - t7199)
  Fix passwd(5) ref and reflect that commit doens't use commit-tree
  improve handling of sideband message display
  tests: use "git xyzzy" form (t3600 - t6999)
  tests: use "git xyzzy" form (t0000 - t3599)
  checkout: fix message when leaving detached HEAD
  clone: fix creation of explicitly named target directory
  'git foo' program identifies itself without dash in die() messages
  setup_git_directory(): fix move to worktree toplevel directory
  update-index: fix worktree setup
  Start conforming code to "git subcmd" style
  read-tree: setup worktree if merge is required
  grep: fix worktree setup
  diff*: fix worktree setup

Conflicts:
	RelNotes
	t/t3900-i18n-commit.sh
	t/t7003-filter-branch.sh