Merge branch 'maint'

Merge branch 'maint'

* maint:
  diff-patch: Avoid emitting double-slashes in textual patch.
  Reword git-am 3-way fallback failure message.
  Limit filename for format-patch
  core.legacyheaders: Use the description used in RelNotes-1.5.0
  git-show-ref --verify: Fail if called without a reference

Conflicts:

	builtin-show-ref.c
	diff.c