Merge branch 'kn/ref-filter-branch-list' into maint

"git for-each-ref --format=..." with %(HEAD) in the format used to
resolve the HEAD symref as many times as it had processed refs,
which was wasteful, and "git branch" shared the same problem.

* kn/ref-filter-branch-list:
  ref-filter: resolve HEAD when parsing %(HEAD) atom

diff --cc ref-filter.c
Simple merge