Merge branch 'jc/diff-filter-negation'

Merge branch 'jc/diff-filter-negation'

Teach "git diff --diff-filter" to express "I do not want to see
these classes of changes" more directly by listing only the
unwanted ones in lowercase (e.g. "--diff-filter=d" will show
everything but deletion) and deprecate "diff-files -q" which did
the same thing as "--diff-filter=d".

* jc/diff-filter-negation:
  diff: deprecate -q option to diff-files
  diff: allow lowercase letter to specify what change class to exclude
  diff: reject unknown change class given to --diff-filter
  diff: preparse --diff-filter string argument
  diff: factor out match_filter()
  diff: pass the whole diff_options to diffcore_apply_filter()