Merge branch 'lc/rebase-trailer'

"git rebase" learns "--trailer" command to drive the interpret-trailers machinery. * lc/rebase-trailer: rebase: support --trailer commit, tag: parse --trailer with OPT_STRVEC trailer: append trailers without fork/exec trailer: libify a couple of functions interpret-trailers: refactor create_in_place_tempfile() interpret-trailers: factor trailer rewriting