Merge branch 'maint'

Merge branch 'maint'

* maint:
  Update draft release notes for 1.6.0.1
  Add hints to revert documentation about other ways to undo changes
  Install templates with the user and group of the installing personality
  "git-merge": allow fast-forwarding in a stat-dirty tree
  completion: find out supported merge strategies correctly
  decorate: allow const objects to be decorated
  for-each-ref: cope with tags with incomplete lines
  diff --check: do not get confused by new blank lines in the middle
  remote.c: remove useless if-before-free test
  mailinfo: avoid violating strbuf assertion
  git format-patch: avoid underrun when format.headers is empty or all NLs