Merge branch 'la/trailer-api'

Merge branch 'la/trailer-api'

Trailer API updates.

Acked-by: Christian Couder <christian.couder@gmail.com>
cf. <CAP8UFD1Zd+9q0z1JmfOf60S2vn5-sD3SafDvAJUzRFwHJKcb8A@mail.gmail.com>

* la/trailer-api:
  format_trailers_from_commit(): indirectly call trailer_info_get()
  format_trailer_info(): move "fast path" to caller
  format_trailers(): use strbuf instead of FILE
  trailer_info_get(): reorder parameters
  trailer: move interpret_trailers() to interpret-trailers.c
  trailer: reorder format_trailers_from_commit() parameters
  trailer: rename functions to use 'trailer'
  shortlog: add test for de-duplicating folded trailers
  trailer: free trailer_info _after_ all related usage