Merge branch 'jk/for-each-ref-multi-key-sort-fix'

Merge branch 'jk/for-each-ref-multi-key-sort-fix'

"git branch" and other "for-each-ref" variants accepted multiple
--sort=<key> options in the increasing order of precedence, but it
had a few breakages around "--ignore-case" handling, and tie-breaking
with the refname, which have been fixed.

* jk/for-each-ref-multi-key-sort-fix:
  ref-filter: apply fallback refname sort only after all user sorts
  ref-filter: apply --ignore-case to all sorting keys